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kassy

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Earth through time
« on: November 30, 2021, 03:55:43 PM »
This is a thread for interesting stuff related to the deep history of planet earth. Think geology, but feathered dinosaurs are fine too, or trilobites.

We start of with the recipe for mountains.  :)

Earth's Ancient Mountains Rose Up With Help From The Ocean's Tiniest Organisms

Without an explosion in ocean life more than 2 billion years ago, many of Earth's mountains might never have formed, according to new research.

When tiny organisms in the shallows of the sea, like plankton, die and sink to the bottom, they can add organic carbon to Earth's crust, making it weaker and more pliable.

A case study of 20 mountain ranges around the world, including those in the Rockies, the Andes, Svalbard, central Europe, Indonesia, and Japan, has now linked the timing of high carbon burial in the ocean with the very generation of our planet's peaks.

"The additional carbon allowed easier deformation of the crust, in a manner that built mountain belts, and thereby plate margins characteristic of modern plate tectonics," the researchers write.

The changes seem to have begun roughly 2 billion years ago, in the middle of the Paleoproterozoic Era, when biological carbon from plankton and bacteria began to add exceptionally high concentrations of graphite to the ocean floor's shale. This made the rock brittle and more likely to stack.

Within 100 million years, most mountain ranges began to form in these weakened slices of crust. Mountain ranges that emerged more recently follow the same pattern.

In the Himalayas, for instance, tectonic thrusting around 50 million years ago was focused on Paleoproterozoic sediments with the most organic-rich beds.

The timing and location implies that biological carbon in graphite continues to shape the geology of our planet.

"Ultimately what our research has shown is that the key to the formation of mountains was life, demonstrating that the Earth and its biosphere are intimately linked in ways not previously understood," explains geologist John Parnell from the University of Aberdeen in Scotland.

The data for the study were collected from already published literature on mountain formation and buried marine biomass.

In the past, numerous studies have shown tectonic plates need to be weakened by graphite to create mountains, but how this initially occurs is less clear.

The new research suggests marine life is a key part of the process. All 20 of the mountain ranges studied ultimately held black shale highly concentrated with graphite, which appeared to come from a biological origin.

"We can see the evidence in the northwest of Scotland, where the roots of the ancient mountains and the slippery graphite that helped build them can still be found, in places like Harris, Tiree, and Gairloch," says Parnell.

The surge in marine life 2 billion years ago most likely occurred in response to the Great Oxidation Event, when photosynthesizing bacteria began to produce vast amounts of oxidation, capable of supporting new forms of single-celled life, like an abundance of marine plankton.

Yet the formation of mountains doesn't even require that much biological carbon. Just a small percentage of biomass is needed for the edges of tectonic plates to slip under or over one another when they collide.

In mountain ranges made from Paleoproterozoic sediment, however, carbon content is consistently above 10 percent. Scientists found it sometimes even reaches above 20 percent.

In short, it seems an exceptional surge in marine life billions of years ago set the stage for many of the mountain ranges we see today.

"As the carbon contents of the sediment were anomalously high in the Paleoproterozoic, the flux of carbon into subduction zones was greater, and hence deformation could take place more readily than had been possible hitherto," the authors explain.

If the team is right, it means microscopic single-celled organisms, invisibly floating in the sea, might have played a key role in creating some of the largest geological structures on our planet.

From the littlest things on Earth, the biggest things can grow.

https://www.sciencealert.com/the-tiniest-organisms-in-the-sea-could-have-helped-build-the-largest-structures-on-land

Open access

Increased biomass and carbon burial 2 billion years ago triggered mountain building
https://www.nature.com/articles/s43247-021-00313-5
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kassy

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Re: Earth through time
« Reply #1 on: December 07, 2021, 10:55:51 AM »
Plankton May Have Escaped ‘Survival of the Fittest’

Scientists have a new theory about why the ocean has so many types of plankton.

There’s a long-standing conundrum in ecology called the paradox of the plankton. Famously articulated by ecologist George Evelyn Hutchinson in 1961, the paradox explores how odd it is that there are thousands of species of phytoplankton in the upper reaches of the ocean. The top few meters of water are basically a well-mixed soup, meaning all of these species of phytoplankton are relying on the same nutrients. The theory of competitive exclusion says that one of these species ought to be a little stronger, and should out-compete the rest. But none has. Why?

Hutchinson published the paradox at the height of the Cold War, when the air was thick with debates over the values of competition and the sharing of resources. Ecological thinking was itself dominated by the idea that competition drives some species to thrive and others to go extinct. But Hutchinson saw this way of thinking as an oversimplification, and he held up phytoplankton as an example of how there must be additional forces shaping biodiversity.

Over the past few decades, ecologists have suggested many explanations for why multiple phytoplankton species persist, including the effects of rapid environmental shifts, the existence of species codependencies, the uneven distributions of phytoplankton species, and the fact that some phytoplankton release toxins that may give them an edge over the competition. But a new study by Oregon State University ecologist Michael Behrenfeld and his colleagues seeks to solve the dilemma by taking a different perspective: the plankton’s.

Phytoplankton are so small, and the distances between them so vast—from their perspective—that it’s likely phytoplankton aren’t competing at all, says Behrenfeld. If you imagine that a phytoplankton is roughly the size of a tree’s root ball, he says, the next nearest phytoplankton would be kilometers away.

A phytoplankton’s small size also means that it experiences water as a thick substance, perhaps akin to how honey feels to us. When an individual phytoplankton moves, a layer of water called the “boundary layer” moves with it. This means that phytoplankton spend most of their time firmly separated from one another.

“When you think of it that way, it’s like, well, how can phytoplankton that are that physically distant actually directly compete with each other?” Behrenfeld says.

and more on:
https://www.theatlantic.com/science/archive/2021/12/how-can-ocean-have-many-types-plankton/620909/

Yes it is quite recent but the problem is 50 years old and plankton has of course been doing this for millions of years.
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Freegrass

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Re: Earth through time
« Reply #2 on: December 07, 2021, 11:44:03 AM »
....all of these species of phytoplankton are relying on the same nutrients. The theory of competitive exclusion says that one of these species ought to be a little stronger, and should out-compete the rest. But none has. Why?

We don't have one plant that dominates the soil either, do we? Grass competes with flowers, as bees compete with other insects... It's just how nature works. We're all fighting for our own existence...

Quote
As organisms that cannot swim against the currents, plankton are intimately connected to their physical environment. Many species are quite sensitive to the temperature, salinity, and nutrient levels that either lead to their proliferation or demise. Physical conditions and nutrient levels can lead to high abundances of particular plankton types. These plankton “blooms” are common throughout the world’s oceans and can be composed of phytoplankton, zooplankton, or gelatinous zooplankton, depending on the environmental conditions.
https://blog.planktonportal.org/2014/03/12/plankton-blooms-causes-and-consequences/
« Last Edit: December 07, 2021, 11:51:12 AM by Freegrass »
90% of the world is religious, but somehow "love thy neighbour" became "fuck thy neighbours", if they don't agree with your point of view.

WTF happened?

squilliam

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Re: Earth through time
« Reply #3 on: December 07, 2021, 12:03:49 PM »
@kassy do you think it has something to do with viral parasitism? If they were all one species or only a few species then they would be much more vulnerable to virons right? I remember reading that parasites and disease are a significant reason for sexual selection in vertebrates.

kassy

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Re: Earth through time
« Reply #4 on: December 08, 2021, 10:14:56 AM »
The whole explanation is in modelling them at their own proper size which is a nice elegant solution.

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Sigmetnow

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Re: Earth through time
« Reply #5 on: December 08, 2021, 05:29:14 PM »
This is a thread for interesting stuff related to the deep history of planet earth. Think geology, but feathered dinosaurs are fine too, or trilobites. …

Sorry, no feathers on this dinosaur.  But it did fly!
Fleshing out the bones of Quetzalcoatlus, Earth's largest flier ever
by Robert Sanders, University of California - Berkeley
Quote
Look around any wetland today and you're likely to see 3-foot-tall egrets or 4-foot-tall herons wading in the shallows in stealthy search of fish, insects or crustaceans.

But 70 million years ago, along the Rio Grande River in Texas, a more impressive and scarier creature stalked the marshes: the 12-foot-tall pterosaur known as Quetzalcoatlus. With a 37- to 40-foot wingspan, it was the largest flying animal that ever lived on Earth.

In six papers published this week as a Memoir by the Society of Vertebrate Paleontology, scientists and an artist provide the most complete picture yet of this dinosaur relative, the largest example of which is represented by just a single set of fossilized bones collected in the late 1970s from Big Bend National Park. The papers describe the pterosaur's geological and ecological setting during the Upper Cretaceous, its anatomy and taxonomic position, and how it moved on the ground and in the air.

One of the papers, co-authored by University of California, Berkeley, paleontologist Kevin Padian, emeritus professor of integrative biology and emeritus curator in the UC Museum of Paleontology, answers some of the mysteries surrounding the flying and walking behavior of this unique animal, about which little has been published since its discovery more than 45 years ago. How can an animal walk with wings so long that they touch the ground when folded? What did it eat, and how did it feed? How strong a flier was it? And how does an animal whose wings span 40 feet, yet whose legs are only 6 feet high at the hip, launch itself into the air?

"This ancient flying reptile is legendary, although most of the public conception of the animal is artistic, not scientific," said Padian, who co-edited the monograph. "This is the first real look at the entirety of the largest animal ever to fly, as far as we know. The results are revolutionary for the study of pterosaurs—the first animals, after insects, ever to evolve powered flight." …

Unlike the serpent god, Quetzalcoatlus had no feathers: Its body, including wings of skin and fibers of keratin, was covered with hair, as in all pterosaurs. Like dinosaurs, it was likely warm- blooded and active. It had lost its tail, presumably to improve its maneuverability, and its 6-foot neck and 4-foot crested skull suggest a stork on steroids. …


The picture that Padian, Cunningham and Conway paint is of an animal similar to egrets and herons in how it feeds and launches itself into the air, like condors and vultures in how it soars, but, because of its enormous wings, unlike any other known animal in how it walks.

"Pterosaurs have huge breastbones, which is where the flight muscles attach, so there is no doubt that they were terrific fliers," he said. "Their upper arm bone—the humerus—has huge, bony crests for anchoring the flight muscles, which are larger than those of birds and far larger than those of bats. The wings worked essentially like those of birds and other dinosaurs, to which pterosaurs are most closely related. Despite two centuries of reconstructing pterosaurs like bats, there is no evidence for this view: Bats are unique and very different from birds and pterosaurs."

Like birds and bats and even humans, the forelimbs of pterosaurs have three segments: the upper arm or humerus, from the shoulder socket to the elbow; the forearm, including the radius and ulna; and the wrist and hand bones. But unlike birds and bats, the leading edge of the outer part of the pterosaur wing is formed by a giant wing-finger.

"It's like having a ski pole extended from the base of your fingers and angled 90 degrees outward," Padian said. …
https://phys.org/news/2021-12-fleshing-bones-quetzalcoatlus-earth-largest.html
People who say it cannot be done should not interrupt those who are doing it.

kassy

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Re: Earth through time
« Reply #6 on: December 08, 2021, 07:22:28 PM »
I read about this earlier today. Cool bit of research even if they took their time.
Back in the days my kids science books did not have them hairy, but not feathered either. Then again they usually depicted dinosaurs from wildly different ages together, although you would only discover that much later.

I remember visiting the London Natural History museum and that had this huge Diplodocus (i think). It was long, it was really long and high and big. Pretty soon we were wondering about it´s droppings.  :)
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kassy

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Re: Earth through time
« Reply #7 on: December 14, 2021, 06:11:08 PM »
THE NEWLY FORMED MOON MAY HAVE TIDALLY HEATED THE EARTH

... if you had seen the rising Moon, oh, say, 4.4 billion years ago, it would've been immense on the horizon. Shortly after it formed it was much, much closer to Earth, and would have appeared 15 times bigger in the sky than it does now.

This, it turns out, may also help solve a long-standing and pernicious astronomical problem: Why wasn't the Earth frozen solid when it was young?

When the Earth was very young, a few million years after it first formed, it was very hot. Certainly after a Mars-sized planet whacked us but good and formed the Moon, the Earth was heated substantially again. But after that it would've cooled.

The thing is, stars like the Sun get hotter with age. Around the time the Moon formed, roughly 70 million years after Earth did, the Sun was only about 70% as luminous as it is today, getting warmer and brighter by roughly 6% every billion years. That means Earth wasn't receiving nearly as much heat then as it is now. The surface should've been frozen.

But we see lots of evidence of liquid water from back then; minerals and rock formations that indicate they were submerged when they formed. Somehow, Earth's temperature remained somewhat stable over the eons despite the Sun getting hotter. This is called the Faint Young Sun Paradox.

...

In a new paper, a team of scientists proposes a significant source of heating may have been the Moon.

...

This tidal effect is enormously dependent on distance. The strength weakens with the cube of the Moon's distance, so double the Moon's distance and the tidal force drops by a factor of 2 x 2 x 2 = 8 times.

Right after it formed, the Moon may have been as close to the Earth as 24,000 kilometers. That's ~15 times closer than its current distance of about 380,000 km. This means that right after it formed the tidal effects would've been staggering, well over 3,000 times what they are now.

...

What they found is that even their most extreme models of tidal heating are small compared to the amount of sunlight absorbed by the Earths surface. But this isn't necessarily a failure. Even a modest amount of tidal energy added could cause geological processes like volcanism to go into overdrive. This happens on Jupiter's moon Io, which has significant tidal heating from Jupiter and is the most volcanically active object in the solar system. Some of the lunar tidal heating models give Earth about the same amount of energy, so it's possible this could've triggered volcanism, releasing greenhouse gases and heat from Earth's interior, which would've aided in warming the planet's surface billions of years ago.

What they find is that at best tidal heating doesn't solve the paradox, but it could still have been a significant contributor to Earth's surface warming. This isn't proof by any means, but more of a call to action for scientists to keep this in mind and look into it more deeply.

https://www.syfy.com/syfy-wire/bad-astronomy-tidal-heating-from-the-young-moon-may-solve-an-astronomical-paradox

This idea is a simple and elegant explanation. I think they are right but we won´t know for a while.
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kassy

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Re: Earth through time
« Reply #8 on: December 19, 2021, 02:39:05 PM »
Explore Evolution on Earth in The Most Comprehensive Tree of Life Ever Created

Spiraling fractal branches draw connections between a staggering 2.2 million living species on Earth in the most comprehensive tree of life ever created.

"It allows people to find their favorite living things, be they golden moles or giant sequoias, and see how evolutionary history connects them together to create a giant tree of all life on Earth," explained University of Oxford evolutionary biologist Yan Wong.

The stunning interactive website OneZoom allows us to explore the relationships between all the flavors of life currently recognized by science.

more details:
https://www.sciencealert.com/explore-evolution-on-earth-in-the-most-comprehensive-tree-of-life-ever-created

And here is the site itself:
https://www.onezoom.org/

Working up from seahorses. Quite fascinating. :)
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kassy

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Re: Earth through time
« Reply #9 on: January 09, 2022, 10:33:15 PM »
NSW farmer's fossil discovery opens window to ancient ecosystems

When New South Wales farmer Nigel McGrath hit heavy rock while ploughing a field, little did he realise he was sowing the seeds of a discovery some 15 million years in the making.

His uncovering of a fossilised leaf, embedded in the rock, opened the door to an extraordinary site that's accelerating our understanding of prehistoric life in Australia.

"Many of the fossils that we are finding are new to science and include trapdoor spiders, giant cicadas, wasps and a variety of fish," said Australian Museum and University of NSW palaeontologist Matthew McCurry.

"Until now, it has been difficult to tell what these ancient ecosystems were like, but the level of preservation at this new fossil site means that even small, fragile organisms [such as] insects turned into well-preserved fossils."

Over the past three years, Dr McCurry, his colleague, Michael Frese, and a team of researchers have been secretly excavating and analysing McGraths Flat near Gulgong on the Central Tablelands, discovering thousands of specimens, including rainforest plants, spiders, fruiting bodies, fish and a bird feather.

Among the insects uncovered were wasps, ants, cicadas, mayflies, beetles, flies and assassin bugs.

The quality of the fossils means interactions between species can also be determined.

Even after all this time, the stomach contents of fish have been preserved, allowing the researchers to determine what was on the menu 15 million years ago.

"We have also found examples of pollen preserved on the bodies of insects so we can tell which species were pollinating which plants," Dr Frese said.

The fossils are of such exceptional quality, McGraths Flat has joined the handful of Lagerstatte sites in Australia.

Lagerstatte sites are sedimentary deposits that exhibit extraordinary fossils with exceptional preservation, sometimes including preserved soft tissues.

...

But, unlike its older cousin, McGraths Flat opens a window to the Miocene epoch, a time of immense change in Australia, when the continent was drifting northwards.

...

https://www.abc.net.au/news/2022-01-08/nsw-farmer-fossil-discovery-opens-window-to-ancient-ecosystems/100745850

This is a very cool snapshot in time.
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kassy

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Re: Earth through time
« Reply #10 on: February 01, 2022, 04:06:10 PM »
Low volcanic temperature ushered in global cooling and the thriving of dinosaurs

Researchers in Japan, Sweden, and the US have unearthed evidence that low volcanic temperatures led to the fourth mass extinction, enabling dinosaurs to flourish during the Jurassic period.

Large volcanic eruptions create climatic fluctuations, ushering in evolutionary changes. Yet it is the volcanic temperature of the eruption that determines whether the climate cools or warms.

Since the emergence of early animals, five mass extinctions have taken place. The fourth mass extinction occurred at the end of the Triassic Period -- roughly 201 million years ago. This mass extinction saw many marine and land animals go extinct, especially large-body, crocodilian-line reptiles known as pseudosuchia. Approximately 60-70% of animal species disappeared. As a result, small bodied dinosaurs were able to grow and prosper.

Scientists think the fourth mass extinction was triggered by the eruptions in the Central Atlantic Magmatic Province -- one of the largest regions of volcanic rock. But the correlation between the eruption and mass extinction has not yet been clarified.

Using analysis of sedimentary organic molecules and a heating experiment, current professor emeritus at Tohoku University, Kunio Kaiho and his team demonstrated how low temperature magma slowly heated sedimentary rocks, causing high sulfur dioxide (SO2) and low carbon dioxide emissions (CO2).

The SO2 gas was distributed throughout the stratosphere, converting to sulfuric acid aerosols. The instantaneous increase of global albedo caused short-term cooling, which could have contributed to the mass extinction.

Kaiho and his team took marine sedimentary rock samples from Austria and the United Kingdom and analyzed the organic molecules and mercury (Hg) in them. They found four discrete benzo[e]pyrene + benzo[ghi]perylene + coronene -Hg enrichments.

The discovery of low coronene in the first enrichment was particularly revealing. The second, third, and fifth mass extinction had high coronene concentrations. A low concentration indicates that low temperature heating caused high SO2 release and global cooling.

...

https://www.sciencedaily.com/releases/2022/01/220131110505.htm

map for CAMP location:
https://en.wikipedia.org/wiki/Central_Atlantic_magmatic_province
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kassy

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Re: Earth through time
« Reply #11 on: February 01, 2022, 04:12:10 PM »
And here we have a very recent snapshot and it is not pretty.

Earth’s sediment cycle during the Anthropocene

Abstract
The global sediment cycle is a fundamental feature of the Earth system, balancing competing factors such as orogeny, physical–chemical erosion and human action. In this Review, values of the magnitudes of several sources and sinks within the cycle are suggested, although the record remains fragmented with uncertainties. Between 1950 and 2010, humans have transformed the mobilization, transport and sequestration of sediment, to the point where human action now dominates these fluxes at the global scale. Human activities have increased fluvial sediment delivery by 215% while simultaneously decreasing the amount of fluvial sediment that reaches the ocean by 49%, and societal consumption of sediment over the same period has increased by more than 2,500%. Global warming is also substantially affecting the global sediment cycle through temperature impacts (sediment production and transport, sea ice cover, glacial ice ablation and loss of permafrost), precipitation changes, desertification and wind intensities, forest fire extent and intensity, and acceleration of sea-level rise. With progressive improvements in global digital datasets and modelling, we should be able to obtain a comprehensive picture of the impacts of human activities and climate warming.

Key points

Sediment production (supply) from anthropogenic soil erosion, construction activities, mineral mining, aggregate mining, and sand and gravel mining from coasts and rivers, has increased by about 467% between 1950 and 2010.

Sediment consumption in the Anthropocene, including from reservoir sequestration, highway development and coal and concrete consumption, has increased by about 2,550% between 1950 and 2010.

Transport of sediment from land to the coastal ocean (via rivers, wind, coastal erosion, and ice loss) has decreased by 23% between 1950 and 2010, whereas transport of fluvial particulates including organic carbon has decreased by 49% over the same period; offsets include increases in sediment delivery by icebergs and glacial melt.

If it were not for sequestration of sediment behind dams, global rivers would have increased their particulate loads by 212% between 1950 and 2010.

Anthropocene impacts on the marine sedimentary environment remain poorly characterized but, on the basis of the resuspension of seafloor sediment from trawling, dredging and land reclamation, anthropogenic transport seems to have increased by 780% between 1950 and 2010.

The Earth’s present Anthropocene sediment load (net land-to-sea sediment delivery and anthropogenic sediment production) exceeds 300 billion tons (Gt) per year, a mass flux that includes a small (<6%) contribution from natural processes.

https://www.nature.com/articles/s43017-021-00253-w
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kassy

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Re: Earth through time
« Reply #12 on: February 06, 2022, 12:44:06 PM »
Did ancient supermountains turbocharge the evolution of life?

Australian researchers have found evidence that supermountains – as tall as the Himalayas and as wide as supercontinents – formed at two critical moments in the evolution of life.

“There’s nothing like these two supermountains today,” says Ziyi Zhu, a PhD candidate at the Australian National University (ANU). “It’s not just their height – if you can imagine the 2,400 km long Himalayas repeated three or four times you get an idea of the scale.”

Zhu is the lead author of a new study published in the journal Earth and Planetary Science Letters, in which she and colleagues used zircons to track when these massive mountains formed.

Their findings fit in with what we know about the supercontinent cycle: the idea that the most fundamental pulse of the planet is the formation and breaking-up of the continents into supercontinents. This cycle appears to operate over 700–800 million years, and the dates these supermountains formed line up with when continents were smashing together into supercontinents.

The first example, called the Nuna Supermountain after the supercontinent that was forming at the time, dates back to between 2,000 and 1,800 million years ago.

“It coincides with the likely appearance of eukaryotes, organisms that later gave rise to plants and animals,” Zhu says.

“The second, known as the Transgondwanan Supermountain, coincides with the appearance of the first large animals 575 million years ago and the Cambrian explosion 45 million years later, when most animal groups appeared in the fossil record.”

According to co-author Professor Jochen Brocks, also from ANU: “What’s stunning is the entire record of mountain building through time is so clear. It shows these two huge spikes: one is linked to the emergence of animals and the other to the emergence of complex big cells.”

This study is an addition to the growing body of evidence that mountains played a crucial role in the rise of life on Earth, an idea first proposed in a 2006 paper also published in Earth and Planetary Science Letters.

Wait, how can mountains influence evolution?
It’s all in the erosion.

When mountains form, they bring elements from deep in Earth’s interior up to the surface. Then, as rain and wind and glaciers wear away at the peaks over millennia, these elements – such as iron and phosphorous – are released and make their way through rivers to the ocean.

This helps drive systems like the climate and carbon cycle, as well as supply nutrients key for the development of life.

It’s thought that for a long time in the planet’s history, life was being “held back” because the nutrients it needed to develop were not in abundance. For example, eukaryotes appeared on Earth about 1.7 billion years ago but didn’t rise to dominance until some 800 million years ago. This time interval is known as the ‘Boring Billion’, because there was almost no advance in evolution.

“The slowing of evolution is attributed to the absence of supermountains during that period, reducing the supply of nutrients to the oceans,” explains co-author Professor Ian Campbell from ANU.

This idea is supported by previous research, which has also suggested that the reason for this hiatus is a lack of mountain formation.

Then, when plate tectonics smashed plates into supercontinents and thrust massive mountain chains up above the surface, a new round of erosion supplied the key ingredients that life needed to take off.

These nutrients may have increased oxygen levels in the atmosphere.

“The early Earth’s atmosphere contained almost no oxygen,” Zhu says. “Atmospheric oxygen levels are thought to have increased in a series of steps, two of which coincide with the supermountains.

“The increase in atmospheric oxygen associated with the erosion of the Transgondwanan Supermountain is the largest in Earth’s history and was an essential prerequisite for the appearance of animals.”

“This study gives us markers,” Campbell says, “so we can better understand the evolution of early, complex life.”


further details:
https://cosmosmagazine.com/earth/earth-sciences/supermountains-turbocharge-evolution-of-life/
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Tor Bejnar

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Re: Earth through time
« Reply #13 on: February 06, 2022, 04:18:51 PM »
Thanks, by the way, Kassy, for this 'continuing education' series.  Similar to this thread's title (and what you've put into it), I like reading about "Our understanding of Earth, through time" (Both 'ancient understandings, middle ages, Age of Discovery (Steno, Hutton, Humboldt, etc.), Wegener's observation/theory, Plate Techtonics' and 'How old is the Earth' as understood by people).
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

Sigmetnow

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Re: Earth through time
« Reply #14 on: February 10, 2022, 07:42:17 PM »
How the Mediterranean Sea came to be

“I recently learned something mindblowing about the geological history of the Mediterranean Sea, and I just can't get it out of my head.
Now I'm going to make it *your* problem too. Sorry.
Hang onto your hat. This is wild.
1/
This is the Strait of Gibraltar, where Europe and Africa reach out to *almost* touch each other.
At this point there's only 13 km/ 8 miles between them - and it's where the Med feeds into the Atlantic.
Imagine if something absurdly Roland-Emmerichy happened & it closed up?
⬇️
2/
No need to imagine - because it actually did.
It's called the Messinian Salinity Crisis, and it happened around 5-6 million years ago:
https://en.wikipedia.org/wiki/Messinian_salinity_crisis
After a presumably colossal tectonic shift, the Pillars of Hercules closed (or more correctly were bridged)....
3/
...and the Mediteranean started drying up. 
After some undetermined period of time, the Mediterranean was empty - evaporated down to a desert & a series of huge, super-salty lakes.
 A vast, salty desert bowl - *kilometres* deep.
(This is not the wild thing.)

4/
The desert bowl of the western Med was also noticeable higher than the east.
You can see this in modern sea floor maps: shallower continental crust in the west, deeper oceanic in the east - connected at the modern-day Strait of Sicily...
And primed for another cataclysm.
⬇️
5/
Before I read about this, I assumed that at some point the Strait of Gibraltar cracked, the water rushed in, and over centuries or millennia, our modern Mediterranean was created.
 That's a manageable thought, right? Epic in scale, but - thinkable.
 That's not what happened.

6/
Modern borehole and siesmic data has uncovered huge grooves through the rock on either side of the Gibraltar Strait - each around 250 metres deep...
And there's a channel along the bed of the sea floor, carved with unimaginable force.
It's around 200km long.
7/
At some point, maybe after a massive earthquake, the landlocked cliffs at the Strait were forced aside and the Atlantic rushed in with *mindboggling* fury.
 Not a waterfall, but a long slope - down which roared up to *100 million cubic metres of water a second*.

8/
I'm keeping the nerdy geological details pretty light here. There's so much, and it's all on an incredible, mindbending scale.
If you want to geek out further, I'll have a newsletter on all this next week. Sign up for free here:
everythingisamazing.substack.com
OK, back to it.
9/
This flood, descending a kilometre to the sea floor, had a thousand times the discharge of the modern Amazon...
And it refilled 90% of the West Med in a YEAR.
This was 5 (or 6) million years ago. Did any of our distant ancestors see it?
Can you imagine their terror?
10/
(One year. Or perhaps even less time. Or perhaps a couple of years!
(The point here is: this DIDN'T take centuries, or even decades. It was terrifyingly fast. 
(It must have seemed like the end of the world.)

11/
If you're disappointed that the breached Straits of Gibraltar didn't form a spectacular waterfall - look to the east of this artist's reconstruction, courtesy of Wikipedia.
Remember that the eastern Med is a lot deeper?
South of Sicily, there's an underwater cliff...
⬇️
12/
The flood roared over it at around 160 miles an hour, forming a waterfall over 1.5km high.
And to the east, the deeper desert bowl of the dessicated Mediterranean started filling with water - rising up to 10 metres a day.
*Not* a typo.
13/
The name for this astounding event is the ZANCLEAN MEGAFLOOD:
https://en.wikipedia.org/wiki/Zanclean_flood
I've put it in All Caps because, what a hilariously epic name. I burst out laughing when I read it.
Anyone searching for a name for their new rock band?
14/
So now I'll leave you to do your own reading - although, if you want my own excitable take on all this, I'll have something in my newsletter next week (everythingisamazing.substack.com/about)
And also? Let me say this very loudly:
AS YOU CAN SEE, GEOLOGY IS NOT BORING.”

From:
https://threadreaderapp.com/thread/1491080740586782720.html
Or
https://twitter.com/mikeachim/status/1491080740586782720

XKCD did a fantastic piece centered around people observing this event. It was super cool, published a frame at a time in like 30 minute increments  https://en.wikipedia.org/wiki/Time_(xkcd)
https://twitter.com/math_vet/status/1491211079523119112

Zanclean Flood of the Mediterranean in Sicily - computer animation
2 min
People who say it cannot be done should not interrupt those who are doing it.

Tor Bejnar

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Re: Earth through time
« Reply #15 on: February 10, 2022, 09:49:11 PM »
Re the opening of the Mediterranean Sea ~5 million years ago:  spectacular,indeed!

A wild cascade rather than a waterfall- waterfalls are vertical, cascades are 'just' steep.  (Cascades can have 'mini-waterfalls' within.) 

Read also about the Black Sea filling around 5 to 9,000 years ago (or maybe 14-19,000 years ago or maybe not much to speak about) - and maybe possibly the source of the "Flood" stories from the Cradle of Civilization environment. https://en.wikipedia.org/wiki/Black_Sea_deluge_hypothesis
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kassy

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Re: Earth through time
« Reply #16 on: March 11, 2022, 08:40:50 AM »
Geologists Have Closely Analyzed Two Bizarre 'Blobs' Detected Deep Inside Earth


Earth's interior is not a uniform stack of layers. Deep in its thick middle layer lie two colossal blobs of thermo-chemical material.

To this day, scientists still don't know where both of these colossal structures came from or why they have such different heights, but a new set of geodynamic models has landed on a possible answer to the latter mystery

These hidden reservoirs are located on opposite sides of the world, and judging from the deep propagation of seismic waves, the blob under the African continent is more than twice as high as the one under the Pacific ocean.

After running hundreds of simulations, the authors of the new study think the blob under the African continent is less dense and less stable than its Pacific counterpart, and that's why it's so much taller.

"Our calculations found that the initial volume of the blobs does not affect their height," explains geologist Qian Yuan from Arizona State University.

"The height of the blobs is mostly controlled by how dense they are and the viscosity of the surrounding mantle."

The Pacific and African blobs were first discovered in the 1980s. In scientific terms, these 'superplumes' are known as large low-shear-velocity provinces (LLSVPs).

Compared to the Pacific LLSVP, the current study found the African LLSVP stretches about 1,000 kilometers higher (621 miles), which supports previous estimates.

This vast height difference suggests both of these blobs have different compositions. How this impacts the surrounding mantle, however, is unclear.

Perhaps the less stable nature of the African pile, for instance, can explain why there is such intense volcanism in some regions of the continent. It could also impact the movement of tectonic plates, which float on the mantle.

Other seismic models have found the African LLSVP stretches up to 1,500 kilometers above the outer core, whereas the Pacific LLSVP reaches 800 kilometers high at max.

In lab experiments that seek to replicate Earth's interior, both the African and Pacific piles appear to oscillate up and down through the mantle.

The authors of the current study say this supports their interpretation that the African LLSVP is probably unstable, and the same could go for the Pacific LLSVP, although their models didn't show this.

The different compositions of the Pacific and African LLSVPs could also be explained by their origins. Scientists still don't know where these blobs came from, but there are two main theories.

One is that the piles are made from subducted tectonic plates, which slip into the mantle, are super-heated and gradually fall downwards, contributing to the blob.

Another theory is that the blobs are remnants of the ancient collision between Earth and the protoplanet Thea, which gave us our Moon.

The theories are not mutually exclusive, either. For instance, perhaps Thea contributed more to one blob; this could be part of the reason why they look so different today.

...

https://www.sciencealert.com/two-weird-blobs-deep-inside-earth-are-surprisingly-different

Nice visual on the link.

It´s interesting they mention Thea (Theia). I always wondered about the role that one played for tectonics.
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kassy

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Re: Earth through time
« Reply #17 on: March 21, 2022, 04:55:31 PM »
Hot springs reveal where continental plates collide beneath Tibet

By analyzing the chemistry of over 200 geothermal springs, researchers have identified where the Indian Plate ends beneath Tibet, debunking some long-debated theories about the process of continental collision.

...

By analyzing the chemistry of over 200 geothermal springs, researchers have identified where the Indian Plate ends beneath Tibet, debunking some long-debated theories about the process of continental collision.

In the classic example of mountain-building, the Indian and Asian continental plates crashed -- and continue colliding today -- to form the world's largest and highest geologic structures: the Himalayan Mountains and the Tibetan Plateau.

Despite the importance of these formations, which influence the global climate through atmospheric circulation and seasonal monsoons, experts have proposed contradicting theories about how tectonic plates below the surface created the iconic behemoths. Now, using geochemical data from 225 hot springs, scientists have mapped the boundary between the Indian and Asian continental plates, shedding light on processes occurring deep below the surface. The findings, which have implications for mineral formation, appear in the current issue of Proceedings of the National Academy of Sciences.

"A principal debate amongst geologists is whether or not continental collision looks like oceanic collision," said senior study author Simon Klemperer, a geophysics professor at Stanford's School of Earth, Energy & Environmental Sciences (Stanford Earth). "Because there are too few measurements, seismology wasn't giving us the answer -- that's why I took up geochemistry as a totally different way to measure things."

Klemperer has spent the better part of a decade traveling to Tibet and India to collect samples to support his theory that chemicals bubbling to the surface could be used to understand what's happening 50 miles below. He and his colleagues tracked down remote geothermal springs for hundreds of miles across the mountains and plateau -- about the distance from Canada to Mexico in the western U.S.

Using the noble gas helium, which doesn't react with other chemicals, the study authors determined which springs originated from each continental plate. One helium isotope signature revealed when the gas came from the hot mantle -- the Asian plate -- while a different signature indicated the much colder Indian plate. The research shows that the colder plate is only detected in the south, beneath the Himalayas, while further north, India is no longer touching Tibet above it -- it's separated from Tibet by a wedge of hot mantle. The results indicate that an old theory that the Indian plate lies flat beneath Tibet is no longer tenable.

"It's amazing that we now have this remarkably well-defined boundary just a few kilometers wide at the surface above a plate boundary that is 100 kilometers deep," Klemperer said.

Subduction vs. collision

In oceanic subduction, material in the subsurface is recycled into the Earth's mantle when the cooler, heavier plate dives under a continental plate and sinks. The process occurs in zones like the Ring of Fire, which is known for frequent earthquakes and active volcanoes.

In continental collision, researchers have hypothesized that subduction of ocean crust dragged the two continents closer together until they collided, closing up the subduction zone for mountain building to occur. This evidence of the continental boundary below Tibet introduces the possibility that the continental crust is releasing fluids and melting -- just as it would happen in oceanic subduction.

"This says that we shouldn't be looking at continental collision and oceanic subduction as two different things -- we should be looking at them as the same thing with somewhat different flavors because geometrically, they look the same," Klemperer said.

And more:
https://www.sciencedaily.com/releases/2022/03/220314154424.htm
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kassy

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Re: Earth through time
« Reply #18 on: March 28, 2022, 03:05:51 AM »
Earth Has a 27.5-Million-Year 'Heartbeat', But We Have No Idea What Causes It

...

A recent study of ancient geological events suggests that our planet has a slow, steady 'heartbeat' of geological activity every 27 million years or so.

This pulse of clustered geological events – including volcanic activity, mass extinctions, plate reorganizations, and sea level rises – is incredibly slow, a 27.5-million-year cycle of catastrophic ebbs and flows. But luckily for us, the research team notes we have another 20 million years before the next 'pulse'.

"Many geologists believe that geological events are random over time," said Michael Rampino, a New York University geologist and the study's lead author, in a 2021 statement.

"But our study provides statistical evidence for a common cycle, suggesting that these geologic events are correlated and not random."

The team conducted an analysis on the ages of 89 well-understood geological events from the past 260 million years.

...

Geologists have been investigating a potential cycle in geological events for a long time. Back in the 1920s and 30s, scientists of the era had suggested that the geological record had a 30-million-year cycle, while in the 1980s and 90s researchers used the best-dated geological events at the time to give them a range of the length between 'pulses' of 26.2 to 30.6 million years.

Now, everything seems to be in order – 27.5 million years is right about where we'd expect. A study published in late 2020 by the same authors suggested that this 27.5-million-year mark is when mass extinctions happen, too.

"This paper is quite good, but actually I think a better paper on this phenomenon was [a 2018 paper by] Muller and Dutkiewicz," tectonic geologist Alan Collins from the University of Adelaide, who wasn't involved in this research, told ScienceAlert in 2021.

That 2018 paper, by two researchers at the University of Sydney, looked at Earth's carbon cycle and plate tectonics, and also came to the conclusion that the cycle is approximately 26 million years long.

Collins explained that in this latest study, many of the events the team looked at are causal – meaning that one directly causes the other, thus some of the 89 events are related: for example, anoxic events causing marine extinction.

"Having said this," he added, "this 26-30 million year cyclicity does seem to be real and over a longer period of time – it also is not clear what is the underlying cause of it!"
...

https://www.sciencealert.com/earth-has-a-27-5-million-year-heartbeat-but-we-have-no-idea-what-causes-it

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kassy

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Re: Earth through time
« Reply #19 on: March 31, 2022, 08:57:28 AM »
More work on the blobs in reply #16.

Billion-year history of Earth’s interior shows it’s more mobile than we thought

...

The blobs may also control the eruption of a kind of rock called kimberlite, which brings diamonds from depths 120-150km (and in some cases up to around 800km) to Earth’s surface.

Scientists have known the blobs existed for a long time, but how they have behaved over Earth’s history has been an open question.

In new research, we modelled a billion years of geological history and discovered the blobs gather together and break apart much like continents and supercontinents.

Scientists generally agree the blobs are linked to the movement of tectonic plates at Earth’s surface. However, how the blobs have changed over the course of Earth’s history has puzzled them.

One school of thought has been that the present blobs have acted as anchors, locked in place for hundreds of millions of years while other rock moves around them. However, we know tectonic plates and mantle plumes move over time, and research suggests the shape of the blobs is changing.

Our new research shows Earth’s blobs have changed shape and location far more than previously thought. In fact, over history they have assembled and broken up in the same way that continents and supercontinents have at Earth’s surface.

We used Australia’s National Computational Infrastructure to run advanced computer simulations of how Earth’s mantle has flowed over a billion years.

These models are based on reconstructing the movements of tectonic plates. When plates push into one another, the ocean floor is pushed down between them in a process known as subduction.

The cold rock from the ocean floor sinks deeper and deeper into the mantle, and once it reaches a depth of about 2000km it pushes the hot blobs aside.

We found that just like continents, the blobs can assemble – forming “superblobs” as in the current configuration – and break up over time.

A key aspect of our models is that although the blobs change position and shape over time, they still fit the pattern of volcanic and kimberlite eruptions recorded at Earth’s surface. This pattern was previously a key argument for the blobs as unmoving “anchors”.

Strikingly, our models reveal the African blob assembled as recently as 60 million years ago – in stark contrast to previous suggestions the blob could have existed in roughly its present form for nearly ten times as long.

Remaining questions about the blobs
How did the blobs originate? What exactly are they made of? We still don’t know.

The blobs may be denser than the surrounding mantle, and as such they could consist of material separated out from the rest of the mantle early in Earth’s history.

This could explain why the mineral composition of the Earth is different from that expected from models based on the composition of meteorites.

Alternatively, the density of the blobs could be explained by the accumulation of dense oceanic material from slabs of rock pushed down by tectonic plate movement.

Regardless of this debate, our work shows sinking slabs are more likely to transport fragments of continents to the African blob than to the Pacific blob.

Interestingly, this result is consistent with recent work suggesting the source of mantle plumes rising from the African blob contains continental material, whereas plumes rising from the Pacific blob do not.

...

https://www.stuff.co.nz/science/300555184/billionyear-history-of-earths-interior-shows-its-more-mobile-than-we-thought

video on the link
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Freegrass

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Re: Earth through time
« Reply #20 on: April 14, 2022, 07:17:41 PM »
Earth is just a little blip in time...

90% of the world is religious, but somehow "love thy neighbour" became "fuck thy neighbours", if they don't agree with your point of view.

WTF happened?

kassy

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Re: Earth through time
« Reply #21 on: April 15, 2022, 07:09:29 PM »
Oops my bad. I mainly wanted this one but i really worded the request wrong:

I was looking for a video on landmass movement, and found many. But then I came across this one. Very interesting, with lots of numbers and information... Would have loved to see it slow down towards the end, because too much information is flashing by too quickly. But you can do that yourself with playback speed. Had to stop the video many times to read some of the events, but I love it. Hope this is a good place to post it. It fits in perfectly with the conversation we're having right now about different states of the earth.


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kassy

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Re: Earth through time
« Reply #22 on: April 15, 2022, 07:55:59 PM »
Further up i posted some animations of Earth tectonics through time but one was a reconstruction that stopped 56 MYA or something like that. I wanted something that ran until now and this video provides it with a tons of extras. I love how it mentions events and has the length of day and the temperature.

Then there are the details. At some point you see volcanic arcs appear. They weren´t the first but the first we can still find rocks from i guess.

The video is really great and some of the comments in the original thread were interesting. I guess it is hard to appreciate geological timescales.

That also makes it even more impressive that there is already more human made stuff then natural biomass all that is a recent thing...
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Laurent

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Re: Earth through time
« Reply #23 on: April 19, 2022, 11:48:54 AM »

kassy

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Re: Earth through time
« Reply #24 on: April 19, 2022, 02:07:13 PM »
Thanks Laurent, those are some really cool links to play with! They give nice control over time and you can drag the planet around.
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kassy

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Re: Earth through time
« Reply #25 on: May 23, 2022, 08:09:59 PM »
Tiny voyagers:


A family of termites has been traversing the world's oceans for millions of years

... much about termites ...

To gain overarching knowledge, the researchers collected hundreds of drywood termite samples from around the world over a timespan of three decades. From this collection, they selected about 120 species, some of which were represented by multiple samples collected in different locations. This represented over a quarter of Kalotermitidae diversity. Most of these samples were brought to OIST where the DNA was isolated and sequenced.

By comparing the genetic sequences from the different species, the researchers constructed an extensive family tree of the drywood termites.

They found that drywood termites have made more oceanic voyages than any other family of termites. They've crossed oceans at least 40 times in the past 50 million years, traveling as far as South America to Africa, which, over a timescale of millions of years, resulted in the diversification of new drywood termite species in the newly colonized places.

"They're very good at getting across oceans," said Dr. Buček. "Their homes are made of wood so can act as tiny ships."

...

The researchers found that most of the genera originated in southern America and dispersed from there. It takes a scale of millions of years for one species to split into several after a move. The research also confirmed that, more recently, dispersals have largely been mediated by humans.

Furthermore, this study has cast doubt on the common assumption that drywood termites have a primitive lifestyle. Among the oldest lineages in the family, there are termite species that do not have a primitive lifestyle. In fact, they can form large colonies across multiple pieces of wood that are connected by tunnels underground.

"This study only goes to highlight how little we know about termites, the diversity of their lifestyles, and the scale of their social lives," stated Prof. Tom Bourguignon, Principal Investigator of OIST's Evolutionary Genomics Unit and senior author of the study. "As more information is gathered about their behavior and ecology, we'll be able to use this family tree to find out more about the evolution of sociality in insects and how termites have been so successful."

https://phys.org/news/2022-05-family-termites-traversing-world-oceans.html
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kassy

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Re: Earth through time
« Reply #26 on: May 29, 2022, 09:17:30 AM »
Dinosaurs' Last Ancient Breaths May Finally Answer a Long-Standing Mystery

Scientists have found a new way to tell whether dinosaurs were hot- or cold-blooded.

...

Early dinosaur researchers initially assumed these animals were slow, lumbering, and cold-blooded like the modern reptiles they seemed to resemble – their closest reptilian relatives that exist today being crocodilians.

More recently, however, there have been hints that this is not the case.

From metabolic clues in eggshells to the warm-blooded trait of being able to withstand frigid polar conditions, there are growing signs that dinosaurs may have been warm-blooded animals.

Some of them are, after all, direct ancestors of the hot-running birds that have the highest metabolism known today.

...

A new method developed by Yale University molecular paleobiologist Jasmina Wiemann now allows researchers to calculate the metabolic rates of dinosaurs using their fossils.

"Metabolism is how effectively we convert the oxygen that we breathe into chemical energy that fuels our body," explains Wiemann. That conversion process makes side products that interact with our bodies' proteins, sugars, and lipids to form chemically stable waste. Animals that are warm-blooded need a higher metabolism to fuel themselves.

It's hard to rely on previous attempts to get metabolic indicators from the knowledge of what temperatures trace minerals in the bones form at because we don't yet understand how the fossilization process alters these minerals. But the stability of the breathing waste product allows it to be fossilized reliably.

Using the femurs of 55 different animals, including dinosaurs, pterosaurs, plesiosaurs, modern birds, mammals, and lizards, the researchers hunted for signs of this telltale molecular waste.

By comparing the amounts of breathing waste found in the bones across these different still-living species, Wiemann and colleagues were able to work out a scale of waste to metabolic rate. Then, they used this to calculate the metabolism of the extinct animals.

"This is really exciting for us as paleontologists – the question of whether dinosaurs were warm- or cold-blooded is one of the oldest questions in paleontology, and now we think we have a consensus, that most dinosaurs were warm-blooded," says Wiemann.

Some, like the lizard-hipped saurischians – which include Triceratops and Stegosaurus – had metabolic rates similar to the cold-blooded reptiles we know today. But many of the other groups ran hot.

Even pterosaurs were warm-blooded, suggesting that endothermy was present in their ornithodiran ancestors before pterosaurs split from their dinosaur relatives. It seems birds' high endothermy is a very ancient trait.

...

https://www.sciencealert.com/dinosaurs-last-ancient-breaths-reveal-if-they-were-cold-or-hot-blooded

So most dinosaurs were warm blooded.
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kassy

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Re: Earth through time
« Reply #27 on: July 10, 2022, 09:47:54 AM »
Dinosaurs took over amid ice, not warmth, says a new study of ancient mass extinction

...

We know that the world was generally hot and steamy during the Triassic Period, which preceded the extinction, and during the following Jurassic, which kicked off the age of dinosaurs. However, a new study turns the idea of heat-loving dinosaurs on its head: It presents the first physical evidence that Triassic dinosaur species -- then a minor group largely relegated to the polar regions -- regularly endured freezing conditions there. The telltale indicators: dinosaur footprints along with odd rock fragments that only could have been deposited by ice. The study's authors say that during the extinction, cold snaps already happening at the poles spread to lower latitudes, killing off the coldblooded reptiles. Dinosaurs, already adapted, survived the evolutionary bottleneck and spread out. The rest is ancient history.

"Dinosaurs were there during the Triassic under the radar all the time," said Paul Olsen, a geologist at Columbia University's Lamont-Doherty Earth Observatory, and lead author of the study. "The key to their eventual dominance was very simple. They were fundamentally cold-adapted animals. When it got cold everywhere, they were ready, and other animals weren't."

...

The authors of the new study cite a third factor: During the eruptions' fiercest phases, they would have belched sulfur aerosols that deflected so much sunlight, they caused repeated global volcanic winters that overpowered high greenhouse-gas levels. These winters might have lasted a decade or more; even the tropics may have seen sustained freezing conditions. This killed uninsulated reptiles, but cold-adapted, insulated dinosaurs were able to hang on, say the scientists.

The researchers' evidence: fine-grained sandstone and siltstone formations left by sediments in shallow ancient lake bottoms in the Junggar Basin. The sediments formed 206 million years ago during the late Triassic, through the mass extinction and beyond. At that time, before landmasses rearranged themselves, the basin lay at about 71 degrees north, well above the Arctic Circle. Footprints found by the authors and others show that dinosaurs were present along shorelines. Meanwhile, in the lakes themselves, the researchers found abundant pebbles up to about 1.5 centimeters across within the normally fine sediments. Far from any apparent shoreline, the pebbles had no business being there. The only plausible explanation for their presence: they were ice-rafted debris (IRD).

Briefly, IRD is created when ice forms against a coastal landmass and incorporates bits of underlying rock. At some point the ice becomes unmoored and drifts away into the adjoining water body. When it melts, the rocks drop to the bottom, mixing with normal fine sediments. Geologists have extensively studied ancient IRD in the oceans, where it is delivered by glacial icebergs, but rarely in lake beds; the Junggar Basin discovery adds to the scant record. The authors say the pebbles were likely picked up during winter, when lake waters froze along pebbly shorelines. When warm weather returned, chunks of that ice floated off with samples of the pebbles in tow, and later dropped them.

"This shows that these areas froze regularly, and the dinosaurs did just fine," said study co-author Dennis Kent, a geologist at Lamont-Doherty.

and more:
https://www.sciencedaily.com/releases/2022/07/220701143118.htm
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kassy

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Re: Earth through time
« Reply #28 on: August 07, 2022, 11:08:51 AM »
450 MILLION YEARS AGO, EARTH’S MAGNETIC FIELD ALMOST COLLAPSED — THE RESULTS WOULD HAVE BEEN APOCALYPTIC

MORE THAN HALF a billion years ago, Earth experienced an almost-complete collapse of its magnetic field. It began in the early Cambrian period. Then, after a period of about 15 million years, the field began to grow again. The cause of that collapse and the bounceback of the field was a mystery. Then, a group of geologists studied rocks from Oklahoma that were created during that time. Magnetic markers in the rocks’ minerals pointed toward an event that began some 550 million years ago. That was before the introduction of multicellular life on our planet.

To understand what happened, look at our planet’s structure. Most of us learn in school that Earth is composed of layers. There’s the crust where you’re sitting reading this right now. Underneath that is the mantle, Earth’s thickest layer. It lies over the molten outer core, which surrounds the solid inner core. That inner core has two parts — an outermost inner core and an innermost inner core. The core region lies some 2900 kilometers beneath the surface. The swirling action of liquid iron in the outer core is what generates our magnetic field. If it weren’t for that activity, we wouldn’t have a protective shield against the solar wind. In fact, without it, our planet might be more like Mars today.

So, what happened in the core? Why did our magnetic field fade to almost 10 percent of its strength and then regenerate again? According to John Tarduno, a professor of geophysics at the University of Rochester in New York, the cause was the formation of Earth’s solid inner core.

“The inner core is tremendously important,” he said. “Right before the inner core started to grow, the magnetic field was at the point of collapse, but as soon as the inner core started to grow, the field was regenerated.”

...

By studying the magnetism locked in those ancient crystals, the researchers determined two new important dates. The first was when the magnetic field began to strengthen after nearly collapsing 15 million years earlier. That rapid regrowth was due to the formation of a solid inner core. It actually recharged the molten outer core and restored the magnetic field’s strength.

Another interesting thing happened about 450 million years ago. That’s when the growing inner core’s structure changed. The result was a boundary between the innermost and outermost inner core. Far above the core, changes to the mantle took place due to plate tectonics on the surface.

...

https://www.inverse.com/science/earths-magnetic-field-almost-collapsed
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kassy

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Re: Earth through time
« Reply #29 on: August 11, 2022, 12:05:13 PM »
Meteorite strikes created Earth’s continents, say scientists

A series of massive meteorite strikes was responsible for the formation of the Earth's continents, a study suggests.

Researchers said on Wednesday that they had found the strongest evidence yet that the continents were held together by ancient geological structures created when vast pieces of space rock ploughed into our planet.

The largest of these meteors were likely to have been more than 100 kilometres in diameter. They would have collided with Earth when it was still relatively young, about 3.5 billion years ago.

The evidence comes in the form of tiny grains of the mineral zircon. An analysis published in the journal Nature suggests that samples recovered from a key region of Western Australia carry the signs of a large meteorite strike.

"Meteorite impacts do everything required to make continents," Tim Johnson, who led the study at Curtin University in Perth, said. "We are extremely excited by these findings."

Over the 4.5 billion years that our planet has existed its appearance has altered dramatically. Roughly 335 million years ago, for instance, three masses of land - known as Gondwana, Euramerica and Siberia - are thought to have come together to form the supercontinent of Pangea.

About 200 million years ago Pangea broke apart, ultimately leading to the continents we know today.

However, even as these changes unfolded, large pieces of the Earth's surface remained intact - a little like pieces of a jigsaw. These are known as "cratons". They are large pieces of ancient crust that have remained stable since long before complex life emerged.

The study involved examining crystals of zircon in rocks from the Pilbara Craton in Western Australia, which is Earth's best-preserved remnant of ancient crust.

"A giant meteorite hitting Earth is a bit like being hit hard on the head by a stone or a golf ball, in that a big lump forms at the site of impact," Johnson said. There would have been several meteorite strikes, Johnson said, each at least tens of kilometres wide. "They were the big bits of rock left over after everything else had accreted [stuck together] to form planets, for example what we find in the asteroid belt between Mars and Jupiter."

As the meteorite strikes the solid outer shell of the Earth - known as the lithosphere - much of the material it hits is vaporised or blasted away from the impact crater, along with the meteorite itself.

This reduces the pressure that had been pushing down on a lower layer, known as the mantle, which lies between the crust and the Earth's core. The result is the creation of a giant "oceanic plateau" - a thick blob-like unit of dark basaltic rock produced by the mantle melting and oozing upwards. Similar structures are seen beneath Hawaii or Iceland - it is why they stick up above sea level, Johnson said.

If an oceanic plateau is large enough, high temperatures at its base will lead to the creation of granite. This has a relatively low density, which means pieces of granite will rise into the plateau and give buoyancy. Roughly speaking, this provides stability, allowing the formation of a continental nucleus.

The latest study is a blow to a competing theory, which suggests that cratons could have been formed by ancient volcanoes. "These findings will upset some people with entrenched views," Johnson said. "That's a good thing, it moves things forward."

https://www.stuff.co.nz/world/300659456/meteorite-strikes-created-earths-continents-say-scientists
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kassy

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Re: Earth through time
« Reply #30 on: August 26, 2022, 09:12:00 AM »
The largest earthquake in human history may have happened 3,800 years ago

Around 1,800 BC, a devastating tsunami wiped out everything unfortunate enough to be on the coast of Chile. The devastation was so severe that it scared hunter-gatherers inland, where they stayed for a thousand years. Now, researchers have tracked the signs of the earthquake that caused the tsunami, and they believe it may have been on the scale of the largest earthquake in recorded history.

...
The main clues for this older earthquake came from tsunami evidence. When a massive earthquake displaces a large volume of water, it can cause a giant wave — a tsunami. Excavations from a 3,800 year-old site on the coastline of Chile showed that hunter-gatherer communities had been destroyed by giant waves. In addition, researchers also found tsunami traces in the Atacama desert.

“The Atacama Desert is one of the driest, most hostile environments in the world and finding evidence of tsunamis there has always been difficult,” explained Prof Goff. “However, we found evidence of marine sediments and a lot of beasties that would have been living quietly in the sea before being thrown inland. And we found all these very high up and a long way inland so it could not have been a storm that put them there.”

By analyzing this data, and carrying out out tsunami modeling studies, the team concludes that the event was caused by a huge, 1,000-km-long megathrust rupture along the Nazca and South American tectonic plates, suggesting that the earthquake may have been of magnitude 9.5 and triggered a huge tsunami.

...

https://www.zmescience.com/science/geology/the-largest-earthquake-in-human-history-may-have-happened-3800-years-ago/
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kassy

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Re: Earth through time
« Reply #31 on: September 02, 2022, 08:53:30 AM »
Land plants changed Earth's composition

Scientists at the University of Southampton have discovered that the evolution of land plants caused a sudden shift in the composition of Earth's continents.

The Southampton researchers, led by Dr Tom Gernon, working with Queen's University Canada, led by Dr Christopher Spencer, and colleagues at the University of Cambridge, the University of Aberdeen, and the China University of Geosciences, Wuhan, studied the effects of land plant evolution on Earth's chemical composition over the past 700 million years.

The researchers' findings are published in the journal Nature Geoscience.

The evolution of land plants took place about 430 million years ago during the Silurian Period, when North America and Europe were conjoined in a landmass called Pangaea.

The proliferation of plants completely transformed Earth's biosphere -- those parts of the planet's surface where life thrives -- paving the way for the advent of dinosaurs about 200 million years later.

"Plants caused fundamental changes to river systems, bringing about more meandering rivers and muddy floodplains, as well as thicker soils," says Dr Christopher Spencer, Assistant Professor at Queen's University in Kingston, Ontario, lead author of the study. "This shift was tied to the development of plant rooting systems that helped produce colossal amounts of mud (by breaking down rocks) and stabilised river channels, which locked up this mud for long periods."

The team recognised that Earth's surface and deep interior are linked by plate tectonics -- rivers flush mud into the oceans, and this mud then gets dragged into the Earth's molten interior (or mantle) at subduction zones where it gets melted to form new rocks.

"When these rocks crystallise, they trap in vestiges of their past history," says Dr Tom Gernon, Associate Professor of Earth Science at the University of Southampton and co-author of the study. "So, we hypothesised that the evolution of plants should dramatically slow down the delivery of mud to the oceans, and that this feature should be preserved in the rock record -- it's that simple."

To test this idea, the team studied a database of over five thousand zircon crystals formed in magmas at subduction zones -- essentially 'time capsules' that preserve vital information on the chemical conditions that prevailed on Earth when they crystallised.

The team uncovered compelling evidence for a dramatic shift in the composition of rocks making up Earth's continents, which coincides almost precisely with the onset of land plants.

Notably, the scientists also found that the chemical characteristics of zircon crystals generated at this time indicate a significant slowing down of sediment transfer to the oceans, just as they had hypothesised.

The researchers show that vegetation changed not only the surface of the Earth, but also the dynamics of melting in Earth's mantle.

"It is amazing to think that the greening of the continents was felt in the deep Earth," concludes Dr Spencer.

"Hopefully this previously unrecognised link between the Earth's interior and surface environment stimulates further study."

https://www.sciencedaily.com/releases/2022/08/220830131636.htm
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kassy

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Re: Earth through time
« Reply #32 on: September 11, 2022, 03:24:54 PM »
Surprising discovery shows a slowing of continental plate movement controlled the timing of Earth's largest volcanic events

Scientists have shed new light on the timing and likely cause of major volcanic events that occurred millions of years ago and caused such climatic and biological upheaval that they drove some of the most devastating extinction events in Earth's history.

Surprisingly the new research, published today in the journal Science Advances, suggests a slowing of continental plate movement was the critical event that enabled magma to rise to the Earth's surface and deliver the devastating knock-on impacts.

Earth's history has been marked by major volcanic events, called Large Igneous Provinces (LIPs) -- the largest of which have caused major increases in atmospheric carbon emissions that warmed Earth's climate, drove unprecedented changes to ecosystems, and resulted in mass extinctions on land and in the oceans.

Using chemical data from ancient mudstone deposits obtained from a 1.5 km-deep borehole in Wales, an international team led by scientists from Trinity College Dublin's School of Natural Sciences was able to link two key events from around 183 million years ago (the Toarcian period).

The team discovered that this time period, which was characterised by some of the most severe climatic and environmental changes ever, directly coincided with the occurrence of major volcanic activity and associated greenhouse gas release on the southern hemisphere, in what is nowadays known as southern Africa, Antarctica and Australia.

On further investigation -- and more importantly -- the team's plate reconstruction models helped them discover the key fundamental geological process that seemed to control the timing and onset of this volcanic event and others of great magnitude.

Micha Ruhl, Assistant Professor in Trinity's School of Natural Sciences, led the team. He said:

"Scientists have long thought that the onset of upwelling of molten volcanic rock, or magma, from deep in Earth's interior, as mantle plumes, was the instigator of such volcanic activity but the new evidence shows that the normal rate of continental plate movement of several centimetres per year effectively prevents magma from penetrating Earth's continental crust.

"It seems it is only when the speed of continental plate movement slows down to near zero that magmas from mantle plumes can effectively make their way to the surface, causing major large igneous province volcanic eruptions and their associated climatic perturbations and mass extinctions.

"Crucially, further assessment shows that a reduction in continental plate movement likely controlled the onset and duration of many of the major volcanic events throughout Earth's history, making it a fundamental process in controlling the evolution of climate and life at Earth's surface throughout the history of this planet."

The study of past global change events, such as in the Toarcian, allows scientists to disentangle the different processes that control the causes and consequences of global carbon cycle change and constrain fundamental Earth system processes that control tipping points in Earth's climate system.

...

https://www.sciencedaily.com/releases/2022/09/220909160317.htm
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kassy

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Re: Earth through time
« Reply #33 on: September 12, 2022, 09:13:24 PM »
Magma and ice


Summary:
Let's pretend it's the Late Cretaceous, roughly 66 to 100 million years ago. We've got dinosaurs roaming the land and odd-looking early species of birds, although the shark as we know it is already swimming in the prehistoric oceans -- which cover 82% of Earth. Redwood trees and other conifers are making their debut, as are roses and flowering plants, and with them come bees, termites and ants. Most of all, it's warm, volcanically active and humid all over the place with nary an ice sheet in sight.

Except, according to a group of scientists from UC Santa Barbara, University of Oregon and University of Manitoba, icy conditions did exist in the region of the South Pole.

"And it wasn't just a single-valley glacier," said UCSB geologist John Cottle, "it was probably multiple glaciers or a large ice sheet." Contrary to our widely held picture of the Late Cretaceous as "hot everywhere," he said, there's evidence that polar ice existed during that period, even at the height of global greenhouse conditions. The geologists' study is published in the journal Nature Communications.

A Prehistoric Puzzle

Fast-forward to today. Let's pretend we're in Antarctica. It's chilly, it's barren, and we're standing near a large grouping of exposed glassy rock along the Transantarctic Mountains, adjacent to the Ross Ice Shelf, called the Butcher Ridge Igneous Complex (BRIC).

"I actually heard about these rocks when I was a grad student 20 or so years ago, and they're just really weird," Cottle said. Remote, even by today's Antarctic exploration standards, the BRIC is unusual because the rocks' composition and formation are uncharacteristic of nearby rock formations, with, among other things, large amounts of glass and layered alteration that indicates significant physical, chemical or environmental events that changed their mineral composition.

Cottle got the chance to finally sample the BRIC on a recent expedition, and in the process of analyzing how it was formed, he and his team encountered an "unusually large amount of water."

"So you have a really hot rock that interacts with water, and as it cools, incorporates it into the glass," he said. "If you look at the composition, then you can tell something about where that water came from. It can exist as hydroxyl, which tells you that it probably came from the magma, or it could be molecular, which means it is probably external."

What they were expecting to see was that the alteration in the rock was caused by the water already in the magma as it cooled. What they found instead was a record of a climate process that was thought not to have existed at the time.

In their spectroscopic analysis of the samples, the researchers determined that while some of the water indeed originated with magma as it plumed upward from Earth's interior, as the molten rock cooled into glass just beneath the Earth's surface, it also incorporated groundwater.

"We determined that most of the water in these rocks is externally derived," Cottle said. "We then measured the oxygen and hydrogen isotopic composition of the water and it matches very well to the composition of Antarctic snow and ice."

To lock in their result, Cottle and team also conducted argon-argon geochronology to date the rock and its alteration.

"The problem is, these rocks are Jurassic, so about 183 million years old," he said. "So when you measure the alteration, what you don't know is when that happened." They were able to recover the age of the rock (Jurassic), but also found a younger age (Cretaceous). "So when these rocks cooled and were altered," he continued, "it also reset the argon isotope as well, and you can match the age of the alteration to the composition of the alteration."

There are other, similar volcanic rocks roughly 700 km north of the BRIC that also have a Cretaceous alteration age, indicating that polar glaciation might have been regionally extensive in Antarctica during that time. "What we'd like to do is go to other places in Antarctica and see if we can determine the scale of the glaciation, if we recover the same results that we've already found," he said.

Finding evidence of large ice sheets dating back to the Cretaceous might not alter our general picture of a hot and humid Earth at that time, Cottle said, "but we would have to think about the Cretaceous and Antarctica quite differently than we do now."

https://www.sciencedaily.com/releases/2022/09/220907143335.htm
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kassy

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Re: Earth through time
« Reply #34 on: October 04, 2022, 09:58:38 AM »
This weeks forecast for the next 300 million years:

Supercomputer model predicts supercontinent to form in Pacific 200-300 million years from now


The world’s next supercontinent will form when the Pacific Ocean closes in 200-300 million years according to new research led by Australia’s Curtin University.

Continents and oceanic rock make up Earth’s crust, or lithosphere, which is a thin shell sitting atop thousands of kilometres of molten rock called the mantle.

Earth’s continents move very slowly over the mantle. The Australasian plate is one of the faster moving ones, creeping northward at around 7 centimetres per year.

...

“Over the past two billion years, Earth’s continents have collided to form a supercontinent every 600 million years, known as the supercontinent cycle,” says Dr Chuan Huang, from Curtin’s Earth Dynamics Research Group and the School of Earth and Planetary Sciences. “This means that the current continents are due to come together again in a couple of hundred of million years’ time.”

Co-author Professor Zheng-Xiang Li, also from Curtin’s School of Earth and Planetary Sciences, tells Cosmos that the “supercontinent cycle” is a mystery.

“It’s a very intriguing question. We don’t really know. Until thirty years ago, we knew of one supercontinent – Pangaea between 200 and 300 million years ago. But, with work over the last thirty years, we realised before Pangea there were two more supercontinents. And they happened in a kind of regular interval – every 600 million years. That’s the observation based on the geological record.”

Li suggests that it could be related to a convection-like rising and falling of hotter and colder molten rock respectively in Earth’s mantle.

“The resulting new supercontinent has already been named Amasia because some believe that the Pacific Ocean will close (as opposed to the Atlantic and Indian oceans) when America collides with Asia,” says Huang. “Australia is also expected to play a role in this important Earth event, first colliding with Asia and then connecting America and Asia once the Pacific Ocean closes.”

Li explains that our understanding of plate tectonics has itself been shifting.

“Twenty-five years ago, most people thought the continents were dragged by the mantle – the floating rock underneath the shell of the Earth’s crust. But now, we know it’s a combination of forces. You have the mantle dragging continents, and the oceanic slabs going into the mantle which acts like a heavy sinker also dragging the continents into the mantle.”

...

https://cosmosmagazine.com/earth/supercontinent-pacific-supercomputer/
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kassy

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Re: Earth through time
« Reply #35 on: November 15, 2022, 11:02:12 AM »
Evolution of tree roots may have driven mass extinctions

Geologists find parallels between ancient, global-scale extinction events and modern threats to Earth's oceans

The evolution of tree roots may have triggered a series of mass extinctions that rocked the Earth's oceans during the Devonian Period over 300 million years ago, according to a study led by scientists at IUPUI, along with colleagues in the United Kingdom.

Evidence for this new view of a remarkably volatile period in Earth's pre-history is reported in the Geological Society of America Bulletin. The study was led by Gabriel Filippelli, Chancellor's Professor of Earth Sciences in the School of Science at IUPUI, and Matthew Smart, a Ph.D. student in his lab at the time of the study.

"Our analysis shows that the evolution of tree roots likely flooded past oceans with excess nutrients, causing massive algae growth," Filippelli said. "These rapid and destructive algae blooms would have depleted most of the oceans' oxygen, triggering catastrophic mass extinction events."

The Devonian Period, which occurred 419 million to 358 million years ago, prior to the evolution of life on land, is known for mass extinction events, during which it's estimated nearly 70 percent of all life on Earth perished.

The process outlined in the study -- known scientifically as eutrophication -- is remarkably similar to modern, albeit smaller-scale, phenomenon currently fueling broad "dead zones" in the Great Lakes and the Gulf of Mexico, as excess nutrients from fertilizers and other agricultural runoff trigger massive algae blooms that consume all of the water's oxygen.

The difference is that these past events were likely fueled by tree roots, which pulled nutrients from the land during times of growth, then abruptly dumped them into the Earth's water during times of decay.

The theory is based upon a combination of new and existing evidence, Filippelli said.

Based upon a chemical analysis of stone deposits from ancient lake beds -- whose remnants persist across the globe, including the samples used in the study from sites in Greenland and off the northeast coast of Scotland -- the researchers were able to confirm previously identified cycles of higher and lower levels of phosphorus, a chemical element found in all life on Earth.

They were also able to identify wet and dry cycles based upon signs of "weathering" -- or soil formation -- caused by root growth, with greater weathering indicating wet cycles with more roots and less weathering indicating dry cycles with fewer roots.

Most significantly, the team found the dry cycles coincided with higher levels of phosphorus, suggesting dying roots released their nutrients into the planet's water during these times.

"It's not easy to peer over 370 million years into the past," said Smart. "But rocks have long memories, and there are still places on Earth where you can use chemistry as a microscope to unlock the mysteries of the ancient world."

In light of the phosphorus cycles occurring at the same time as the evolution of the first tree roots -- a feature of Archaeopteris, also the first plant to grow leaves and reach heights of 30 feet -- the researchers were able to pinpoint the decay of tree roots as the prime suspect behind the Devonian Periods extinction events.

Fortunately, Filippelli said, modern trees don't wreak similar destruction since nature has since evolved systems to balance out the impact of rotting wood. The depth of modern soil also retains more nutrients compared to the thin layer of dirt that covered the ancient Earth.

...

https://www.sciencedaily.com/releases/2022/11/221109124317.htm
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Re: Earth through time
« Reply #36 on: November 29, 2022, 01:10:05 PM »
Quote
This is the preserved shell of a giant 'ancient armadillo' creature called Glyptodont that roamed the earth around 20,000 years ago. A farmer in Argentina uncovered four of them in a dried-out riverbed near Buenos Aires in February 2020 [read more: ow.ly/cifl50B0cTo ]
https://twitter.com/rainmaker1973/status/1597145774852145152
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kassy

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Re: Earth through time
« Reply #37 on: December 24, 2022, 11:23:37 AM »
Early forests did not significantly change the atmospheric CO2


Scientists have discovered that the atmosphere contained far less CO2 than previously thought when forests emerged on our planet, the new study has important implications for understanding how land plants affect the climate.

...

Earth's continents were colonized by tall trees and forests about 385 million years ago. Before then, shallow shrub-like plants with vascular tissue, stems, shallow roots, and no flowers had invaded the land. Textbooks tell us that the atmosphere at that time had far higher CO2 levels than today and that an intense greenhouse effect led to a much warmer climate. The emergence of forests was previously thought to promote CO2 removal from the atmosphere, driving the Earth into a long cool period with ice cover at the poles.

Reconstructing atmospheric CO2 levels in the geological past is difficult and has previously relied on proxies that also depend on parameters that had to be assumed. Climate scientists agree that CO2 plays a crucial role in shaping Earth's climate both today and in the past. Therefore, a grand challenge for Earth scientist is to understand what has controlled the abundance CO2 in the atmosphere.

"We calibrated a mechanistic model for the gas-exchange between plant leaves and the ambient air to the oldest lineage of vascular land plants, namely clubmosses. With this approach, we could calculate the CO2 level in the air solely from observations made on the plant material," tells associate professor Tais W. Dahl from the Globe institute at University of Copenhagen, who led the study in collaboration with an international team of researchers from Germany, Saudi Arabia, UK, and USA.

The new method builds on three observations that can be made both in living plants and fossil plant tissue, including the ratio of two stable carbon isotopes and the size and density of stomata (pore openings) through which CO2 is taken up by the plant. The researchers calibrated the method in living clubmosses and found that this approach can accurately reproduce ambient CO2 levels in the greenhouse.

"The newly calibrated method to study CO2 levels from the geological record is superior to previous approaches that produce estimates with unbound error bars simply because they depend on parameters that cannot be independently constrained in the geological record," says Barry Lomax Professor at University of Nottingham and a co-author on the study.

The research team applied the method to some of the oldest vascular plant fossils that lived before and after trees evolved on our planet and discovered that the ratio of the two stable carbon isotopes, carbon-13 and carbon-12, is very similar to that of modern plants. Further, the stomata density and size were also very similar to that observed in their living descendants. These observations kickstarted a more thorough investigation of the early CO2 record.

Dahl and colleagues collected data from 66 fossils of three distinct species of club mosses found in 9 different localities worldwide 410 to 380 million years in age. In all cases, the atmospheric CO2 levels were only 30-70% higher (~525 -- 715 ppm) than today (~415 ppm). This is far lower than previously thought (2000-8000 ppm). Ppm stands for parts-per-million and is the unit used to measure carbon dioxide concentrations in air.

The team utilized a paleoclimate model to show that Earth was a temperate planet with mean tropical surface air temperatures of 24.1-24.6°C.

"We used a fully coupled atmosphere-ocean model to find that Earth had ice-covered poles when forests emerged. Yet, land plants could thrive in the tropical, subtropical and temperate zones," explains Georg Feulner from the Potsdam Institute for Climate in Germany, who co-authored the study.

The new study suggest that trees actually play an insignificant role on atmospheric CO2 levels over longer time scales because early trees had deeper root systems and produced more developed soils that are associated with lower nutrient loss. With more efficient nutrient recycling in soils, trees actually have a smaller weathering demand than the shallow shrub-like vegetation that came before them. This idea goes against previous thinking that trees with deeper root system promoted CO2 removal through enhanced chemical weathering and dissolution of silicate rocks.

Dahl and colleagues used Earth system models to show that primitive shrub-like vascular plants could have caused a massive decline in atmospheric CO2 earlier in history, when they first spread on the continents. The model shows that vascular ecosystem would have simultaneously led to a rise in atmospheric O2 levels.

https://www.sciencedaily.com/releases/2022/12/221220112418.htm

1) This contrast nicely with the tree roots story above.
2) I wonder if we could repeat this for other times of high CO2 to see what the values at the time were.

This could the lead to recalibrating the amount of change to the actual CO2 values to better work out how much of the warming is CO2 and how much planets systems responses.
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kassy

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Re: Earth through time
« Reply #38 on: January 26, 2023, 07:00:27 PM »
Malformed seashells, ancient sediment provide clues about Earth's past

Nearly 100 million years ago, the Earth experienced an extreme environmental disruption that choked oxygen from the oceans and led to elevated marine extinction levels that affected the entire globe.

Now, in a pair of complementary new studies, two Northwestern University-led teams of geoscientists report new findings on the chronology and character of events that led to this occurrence, known as Ocean Anoxic Event 2 (OAE2), which was co-discovered more than 40 years ago by late Northwestern professor Seymour Schlanger.

By studying preserved planktonic microfossils and bulk sediment extracted from three sites around the world, the team collected direct evidence indicating that ocean acidification occurred during the earliest stages of the event, due to carbon dioxide (CO2) emissions from the eruption of massive volcanic complexes on the sea floor.

In one of the new studies, the researchers also propose a new hypothesis to explain why ocean acidification led to a strange blip of cooler temperatures (dubbed the "Plenus Cold Event"), which briefly interrupted the otherwise intensely hot greenhouse period.

By analyzing how an influx of CO2 from volcanoes affected ocean chemistry, biomineralization and climate, the researchers hope to better understand how today's Earth is responding to an increase of CO2 due to human activities, which potentially could lead to solutions for adapting to and mitigating anticipated consequences.

A paper, with findings from deep-sea cores, including a newly drilled site near southwest Australia, will be published on Thursday (Jan. 19) in the journal Nature Geoscience. A complementary paper detailing findings from ancient malformed microfossils was published on Dec. 13, in the Nature journal Communications Earth & Environment.

"Ocean acidification and anoxia resulted from massive CO2 release from volcanoes," said Northwestern's Brad Sageman, a senior co-author of both studies. "These major CO2 emission events in Earth's history provide the best examples we have of how the Earth system responds to very large inputs of CO2. This work has fundamental applicability to our understanding of the climate system, and our ability to predict what will happen in the future."

"Based on isotopic analyses of the element calcium, we propose a possible explanation for the Plenus Cold Event, which is that a slowdown in biocalcification rates due to ocean acidification allowed alkalinity to accumulate in seawater," said Northwestern's Andrew Jacobson, a senior co-author of both studies. "Increased alkalinity led to a drawdown of CO2 from the atmosphere. It could very well be the case that such cooling is a predictable -- but transitory -- consequence of warming. Our results for OAE2 provide a geological analog for ocean alkalinity enhancement, which is a leading strategy for mitigating the anthropogenic climate crisis."

Experts on climate during the Cretaceous Period and isotope geochemistry, Sageman and Jacobson are both professors of Earth and planetary sciences in Northwestern's Weinberg College of Arts and Sciences. The two studies were led by their former Ph.D. students, Gabriella Kitch and Matthew M. Jones, who initiated this research while at Northwestern.

Reconstructing Cretaceous conditions

Based on over 40 years of study, OAE2 is one of the most significant perturbations of the global carbon cycle to have occurred on planet Earth. Researchers have hypothesized that oxygen levels in the oceans dropped so low during OAE2 that marine extinction rates increased significantly. To better understand this event and the conditions leading up to it, the researchers studied ancient organic carbon-rich and fossil-bearing layers of sedimentary rock in widely distributed outcrop sites, as well as deep-sea cores obtained by the International Ocean Discovery Program (IODP) (funded by the National Science Foundation and its international partners).

The sites included Gubbio, Italy (a famous area in mainland Italy that used to be a deep ocean basin), the Western Interior Seaway (an ancient seabed stretching from the Gulf of Mexico to the Arctic Ocean in North America) and a several deep-sea sites, including a new one from the eastern Indian Ocean, offshore of southwest Australia.

Deep-sea cores provide an invaluable record of conditions in parts of the paleo-oceans that were completely unknown prior to the development of ocean drilling programs. In all three cores, the researchers focused on sections from the mid-Cretaceous Period, just before the boundary of the Turonian and Cenomanian Ages, in order to reconstruct conditions leading up to OAE2.

"The challenging part of studying ocean acidification in the geologic past is that we don't have ancient seawater," said Jones, who is now a Peter Buck Postdoctoral Fellow at the Smithsonian Institution. "It's extremely rare that you would find anything that resembles ancient seawater trapped in a rock or mineral. So, we have to look for indirect evidence, particularly changes in the chemistry of fossil shells and lithified sediments."

Malformed fossils

For the study published in Communications Earth & Environment, Kitch and her co-authors focused on fossilized foraminifera, ocean-dwelling unicellular organisms with an external shell made of calcium carbonate, which were collected at the Gubbio site by an Italian collaborator, Professor Rodolfo Coccioni at the University of Urbino.

Kitch and her collaborators were drawn to the Gubbio specimens because Coccioni's optical observations and measurements of their shells showed abnormalities, including a consistent pattern of "dwarfing," or a decrease in overall size, coincident with the onset of OAE2.

"These are optical signs of stress," said Kitch, who is now a Knauss Fellow at the National Oceanic and Atmospheric Administration. "We hypothesized that the stress could have been caused by ocean acidification, which then affected the way the organisms built their shells."

To test this hypothesis, Kitch analyzed the calcium isotope composition of the fossils. After dissolving the fossilized shells and analyzing their composition with a thermal ionization mass spectrometer, the Northwestern team observed that calcium isotope ratios shifted in the malformed specimens in a way consistent with stress from acidification.

"This is the first paper to marry calcium isotopic evidence for acidification with observations of biological indicators of stress," Sageman said. "It's these independent biological and geochemical observations that confirm there was an impact on biomineralization during the onset of OAE2."

'Cause-and-effect relationship'

For the second study, published in Nature Geoscience, Jones and his co-authors focused on deep sea cores of lithified sediments from offshore southwest Australia, which he and colleagues collected during an IODP expedition in 2017. For this piece of the puzzle, the researchers were less interested in what was in the sediment and more interested in what the sediment was noticeably lacking.

The core contains stacks of limestone, rich with calcium carbonate minerals, but is punctuated by a sudden absence of carbonate right before OAE2.

"For this time interval, we found that calcite is absent," Jones said. "There are no carbonate minerals. This section of the core is visibly darker; it jumped right out at us. The carbonate either dissolved at the seafloor or fewer organisms were making calcium carbonate shells in the surface water. It's a direct observation of an ocean acidification event."

In his geochemical analyses conducted in collaboration with Professor Dave Selby at Durham University, Jones noticed that carbonate was not the only component showing significant change. Coincident with the onset of OAE2, there is also a marked shift in osmium isotope ratios that signal a massive input of mantle-derived osmium, the fingerprint of a major submarine volcanism event. This observation is consistent with the work of many other researchers, who have found evidence for the eruption of a large igneous province (LIP) preceding OAE2.

These events of massive volcanic activity occur throughout Earth history and are increasingly recognized as major agents of global change. Many LIPs were submarine, injecting tons of CO2 directly into the oceans. When CO2 dissolves into seawater, it forms a weak acid that can inhibit calcium carbonate formation and may even dissolve preexisting carbonate shells and sediments.

"Right at the onset of OAE2, osmium isotope ratios shift to really, really low values," Jones said. "The only way that can happen is through a large igneous province eruption. That helps us establish a cause-and-effect relationship. We can see the evidence that volcanoes were really active because the osmium values crash. Then, suddenly, there's no carbonate."

Biological feedback

While ocean acidification following a LIP is not necessarily surprising, the Northwestern team did uncover something unusual. Acidic conditions during OAE2 lasted much longer than other widely recognized acidification events in the ancient world. Jones posits that the lack of oxygen in ocean waters may have extended the acidification state.

"Organisms that consumed sinking plankton and organic matter in the water column during OAE2 were also respiring CO2, which contributed to the ocean acidification that was initially triggered by CO2 emission from LIP volcanic activity," Jones said. "So, marine anoxia can be a 'positive feedback' on ocean acidification. That's important because the global ocean today, in addition to having its pH levels decrease, is losing oxygen content as well. That suggests that decreases in oxygen may prolong acidification and highlights that the two phenomena are closely related."

In Kitch's study, she found that biology played yet another role during the event. Global warming and ocean acidification did not just passively affect foraminifera. The organisms also actively responded by reducing calcification rates when building their shells. As calcification slowed, the foraminifera consumed less alkalinity from seawater, which helped buffer the ocean's increasing acidity. This also heightened the ocean's ability to absorb CO2, potentially triggering the Plenus Cold Event.

"We call this phase a 'hothouse period' because temperatures were really, really warm," Kitch said. "However, there is evidence for relative cooling during the OAE2 interval. No one has been able to explain why this cooling happened. Our study shows that by decreasing carbonate production in the ocean, you actually bump up alkalinity, which gives the ocean a buffering capacity to absorb CO2. The ocean suddenly has the capacity to draw down CO2 and balance carbon fluxes."

...

https://www.sciencedaily.com/releases/2023/01/230119112821.htm
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Sigmetnow

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Re: Earth through time
« Reply #39 on: January 28, 2023, 08:16:01 PM »
—- No, the Earth’s core has not stopped spinning
Quote
Corey S. Powell @coreyspowell
If you saw this headline, [⬇️ see below] or one like it, you might reasonably have thought the world has gone mad. The inside of the Earth is spinning backwards?
*But that is not at all what the actual research says.*

[a short thread] #RealityCheck
  —
Key point: Earth's core rotates at almost exactly the same rate as the rest of the planet. Did in the past, still does so now. It rotates at the same speed to within 0.001%!
But even the research paper is confusing on that point: #RealityCheck
nature.com/articles/s4156…  pic.twitter.com/9RcpD5ydoj
  —
What's interesting here is that Earth's inner core rotates *almost* the same as the surface, but not *exactly* the same. It may rotate a tiny bit faster or slower -- and that's not apocalyptic, but it sure is interesting.
sciencenews.org/article/earth-… #Earth #Core pic.twitter.com/DkJ7hlPden
 —
The first hint that Earth's core goes its own way came in 1996. The core appeared to be turning 1 part in 100,000 faster than the surface. That small difference would case it to drift by 10s of kilometers a year -- a big effect by geophysical standards.
nature.com/articles/38222…  pic.twitter.com/qK3QjkI24P
  —
Earth's inner core is solid, but the outer core is liquid. That means the inner core is suspended in liquid, like the insides of a chocolate-covered cherry, leaving it weirdly free to move around. #Core #BeFree  pic.twitter.com/ionFDmD3qM [⬇️ See below ]
  —
Why would Earth's core spin (slightly!) faster or slower than the surface? 1) the gravity of the mantle is pulling on it. 2) magnetic fields from the outer core grab onto it. If we can measure these effects, we learn a lot about the geomagnetic field that keeps us all safe. #Core
pic.twitter.com/XtFSN4cUor
  —
Bottom line: Earth's core cannot just stop rotating and reverse itself! We're talking *tiny* variations, with the rotation period of the core running less than one second faster or slower than it is up top.
Enough to be fascinating, but not enough to do this: #TheCore [fin]
pic.twitter.com/OHeCvdTlBU [Movie poster]
 
1/24/23 https://twitter.com/coreyspowell/status/1617907735022145536

 
< Is this phenomenon in some way related to the ‘shifting’ of the magnetic North Pole?
 
Corey S. Powell @coreyspowell
The drifting of magnetic north is thought to be caused by currents in the fluid outer core, but the inner & outer cores are magnetically coupled, so there's surely some connection. And honestly, the details of what's going on down there are very poorly understood.
1/24/23, 11:43 PM. https://twitter.com/coreyspowell/status/1618107333267329025
People who say it cannot be done should not interrupt those who are doing it.

kassy

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Re: Earth through time
« Reply #40 on: January 28, 2023, 10:50:11 PM »
Mercury helps to detail Earth's most massive extinction event


The Latest Permian Mass Extinction (LPME) was the largest extinction in Earth's history to date, killing between 80-90% of life on the planet, though finding definitive evidence for what caused the dramatic changes in climate has eluded experts.

An international team of scientists, including UConn Department of Earth Sciences researchers Professor and Department Head Tracy Frank and Professor Christopher Fielding, are working to understand the cause and how the events of the LPME unfolded by focusing on mercury from Siberian volcanoes that ended up in sediments in Australia and South Africa. The research has been published in Nature Communications.

Though the LPME happened over 250 million years ago, there are similarities to the major climate changes happening today, explains Frank:

"It's relevant to understanding what might happen on earth in the future. The main cause of climate change is related to a massive injection of carbon dioxide into the atmosphere around the time of the extinction, which led to rapid warming."

In the case of the LPME, it is widely accepted that the rapid warming associated with the event is linked to massive volcanism occurring at a huge deposit of lava called the Siberian Traps Large Igneous Province (STLIP), says Frank, but direct evidence was still lacking.

Volcanos leave helpful clues in the geological record. With the outpouring of lava, there was also a huge quantity of gases released, such as CO2 and methane, along with particulates and heavy metals that were launched into the atmosphere and deposited around the globe.

"However, it's hard to directly link something like that to the extinction event," says Frank. "As geologists, we're looking for a signature of some kind -- a smoking gun -- so that we can absolutely point to the cause."

In this case, the smoking gun the researchers focused on was mercury, one of the heavy metals associated with volcanic eruptions. The trick is finding areas where that record still exists.

...

Not all terrains around the world have such massive gaps in the geologic record, and previous studies of the LPME have focused primarily on sites found in the northern hemisphere. However, the Sydney Basin in Eastern Australia and the Karoo Basin in South Africa are two areas in the southern hemisphere that happen to have an excellent record of the event, and are areas Frank and Fielding have studied previously. A colleague and co-author, Jun Shen from the State Key Laboratory of Geological Processes and Mineral Resources at the China University of Geosciences, reached out and connected with Frank, Fielding, and other co-authors for samples, with hopes to analyze them for mercury isotopes.

Shen was able to analyze the mercury isotopes in the samples and tie all the data together says Frank.

"It turns out that volcanic emissions of mercury have a very specific isotopic composition of the mercury that accumulated at the extinction horizon. Knowing the age of these deposits, we can more definitively tie the timing of the extinction to this massive eruption in Siberia. What is different about this paper is we looked not only at mercury, but the isotopic composition of the mercury from samples in the high southern latitudes, both for the first time."

This definitive timing is something that scientists have been working on refining, but as Fielding points out, the more that we learn, the more complicated it gets.

"As a starting point, geologists have pinpointed the timing of the major extinction event at 251.9 million years with a high degree of precision from radiogenic isotope dating methods. Researchers know that is when the major extinction event happened in the marine environment and it was just assumed that the terrestrial extinction event happened at the same time."

In Frank and Fielding's previous research, they found that the extinction event on land happened 200-600,000 years earlier, however.


"That suggests that the event itself wasn't just one big whammy that happened instantaneously. It wasn't just one very bad day on Earth, so to speak, it took some time to build and this feeds in well into the new results because it suggests the volcanism was the root cause," says Fielding. "That's just the first impact of the biotic crisis that happened on land, and it happened early. It took time to be transmitted into the oceans. The event 251.9 million years ago was the major tipping point in environmental conditions in the ocean that had deteriorated over some time."

Retracing the events relies on knowledge from many different geologists all specializing in different methods, from sedimentology, geochemistry, paleontology, and geochronology, says Frank,

"This type of work requires a lot of collaboration. It all started with fieldwork when a group of us went down to Australia, where we studied the stratigraphic sections that preserved the time interval in question. The main point is that we now have a chemical signature in the form of mercury isotope signatures, that definitively ties the extinction horizon in these terrestrial sections that provide a record of what was happening on land due to Siberian Traps volcanism."

https://www.sciencedaily.com/releases/2023/01/230127131139.htm
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kassy

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Re: Earth through time
« Reply #41 on: February 25, 2023, 06:43:20 PM »
This article covers most of Earth through time in big steps:

The Seven-Ages of Earth as Seen Through the Continental Lens:

The long-term record of Earth’s evolution is preserved in its continental crust. However, this rock archive is limited, and our understanding of the past decreases with increasing age and depth. A recent article in Reviews of Geophysics uses accessible data preserved in this record to identify seven stages in Earth’s history – each marked by a distinct tectonic style or geological events. We asked the authors to give an overview of the Earth’s lithosphere, what these tectonic modes tell us, and what questions remain.

...

What are the key moments in the history of continental lithosphere identified so far?

There would be four fundamental moments in the history of continental lithosphere that may have changed the course of Earth’s evolution. First was when granitoid-dominated felsic crust (i.e., the continental crust) started to appear for the first time. Although there is debate about the timing of it, current consensus is that it happened sometime during 3.8-3.2 Ga.

The second moment would be when the stable continental lithospheres (i.e., the cratons) developed. Based on the record available, this process may have started at ca. 3.2 Ga and may have continued till the end of Archean (2.5 Ga). This process established the nuclei of continents that later grew and were modified through tectonic processes into their current configuration, on which we are living today.

The third critical moment would be when exposure of continental crust above sea level first became widespread. The timing of this event is also not accurately known but from the sedimentary rocks and isotopic evidence, we think this may have happened some 3.2-3.0 billion years ago and continued till the end of Archean, like the evolution of cratons. The emergence of continental crust kickstarted terrestrial weathering and fluvial runoffs that fundamentally changed the composition of atmosphere and oceans, started providing climate feedbacks, and created new habitats for the proliferation of early life.

The final key event was the formation of supercontinents, involving the cyclic amalgamation and dispersal of continental lithosphere, which is a manifestation of global plate tectonics. Again, the timing of this is debated, but most agree it has operated since the Archean (the last 2.5 billion years), with initial signs beginning in the latter half of the Archean (ca. 3.2 billion years ago).

...

https://eos.org/editors-vox/the-seven-ages-of-earth-as-seen-through-the-continental-lens
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kassy

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Re: Earth through time
« Reply #42 on: March 04, 2023, 09:52:35 PM »
Scientists Reveal The Most Detailed Geological Model of Earth's Past 100 Million Years

...

Ours is the first dynamic model – a computer simulation – of the past 100 million years at a high resolution down to 10 kilometers (6.2 miles).

In unprecedented detail, it reveals how Earth's surface has changed over time, and how that has affected the way sediment moves around and settles.

Broken into frames of a million years, our model is based on a framework that incorporates plate tectonic and climatic forces with surface processes such as earthquakes, weathering, changing rivers, and more.

With video on:
https://www.sciencealert.com/scientists-reveal-the-most-detailed-geological-model-of-earths-past-100-million-years
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kassy

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Re: Earth through time
« Reply #43 on: May 27, 2023, 09:03:03 AM »
Iron-rich rocks unlock new insights into Earth's planetary history


Visually striking layers of burnt orange, yellow, silver, brown and blue-tinged black are characteristic of banded iron formations, sedimentary rocks that may have prompted some of the largest volcanic eruptions in Earth's history, according to new research from Rice University.

The rocks contain iron oxides that sank to the bottom of oceans long ago, forming dense layers that eventually turned to stone. The study published this week in Nature Geoscience suggests the iron-rich layers could connect ancient changes at Earth's surface -- like the emergence of photosynthetic life -- to planetary processes like volcanism and plate tectonics.

In addition to linking planetary processes that were generally thought to be unconnected, the study could reframe scientists' understanding of Earth's early history and provide insight into processes that could produce habitable exoplanets far from our solar system.

"These rocks tell -- quite literally -- the story of a changing planetary environment," said Duncan Keller, the study's lead author and a postdoctoral researcher in Rice's Department of Earth, Environmental and Planetary Sciences. "They embody a change in the atmospheric and ocean chemistry."

Banded iron formations are chemical sediments precipitated directly from ancient seawater rich in dissolved iron. Metabolic actions of microorganisms, including photosynthesis, are thought to have facilitated the precipitation of the minerals, which formed layer upon layer over time along with chert (microcrystalline silicon dioxide). The largest deposits formed as oxygen accumulated in Earth's atmosphere about 2.5 billion years ago.

"These rocks formed in the ancient oceans, and we know that those oceans were later closed up laterally by plate tectonic processes," Keller explained.

The mantle, though solid, flows like a fluid at about the rate that fingernails grow. Tectonic plates -- continent-sized sections of the crust and uppermost mantle -- are constantly on the move, largely as a result of thermal convection currents in the mantle. Earth's tectonic processes control the life cycles of oceans.

"Just like the Pacific Ocean is being closed today -- it's subducting under Japan and under South America -- ancient ocean basins were destroyed tectonically," he said. "These rocks either had to get pushed up onto continents and be preserved -- and we do see some preserved, that's where the ones we're looking at today come from -- or subducted into the mantle."

Because of their high iron content, banded iron formations are denser than the mantle, which made Keller wonder whether subducted chunks of the formations sank all the way down and settled in the lowest region of the mantle near the top of Earth's core. There, under immense temperature and pressure, they would have undergone profound changes as their minerals took on different structures.

"There's some very interesting work on the properties of iron oxides at those conditions," Keller said. "They can become highly thermally and electrically conductive. Some of them transfer heat as easily as metals do. So it's possible that, once in the lower mantle, these rocks would turn into extremely conductive lumps like hot plates."

Keller and his co-workers posit that regions enriched in subducted iron formations might aid the formation of mantle plumes, rising conduits of hot rock above thermal anomalies in the lower mantle that can produce enormous volcanoes like the ones that formed the Hawaiian Islands. "Underneath Hawaii, seismological data show us a hot conduit of upwelling mantle," Keller said. "Imagine a hot spot on your stove burner. As the water in your pot is boiling, you'll see more bubbles over a column of rising water in that area. Mantle plumes are sort of a giant version of that."

"We looked at the depositional ages of banded iron formations and the ages of large basaltic eruption events called large igneous provinces, and we found that there's a correlation," Keller said. "Many of the igneous events -- which were so massive that the 10 or 15 largest may have been enough to resurface the entire planet -- were preceded by banded iron formation deposition at intervals of roughly 241 million years, give or take 15 million. It's a strong correlation with a mechanism that makes sense."

The study showed that there was a plausible length of time for banded iron formations to first be drawn deep into the lower mantle and to then influence heat flow to drive a plume toward Earth's surface thousands of kilometers above.

In his effort to trace the journey of banded iron formations, Keller crossed disciplinary boundaries and ran into unexpected insights.

"If what's happening in the early oceans, after microorganisms chemically change surface environments, ultimately creates an enormous outpouring of lava somewhere else on Earth 250 million years later, that means these processes are related and 'talking' to each other," Keller said. "It also means it's possible for related processes to have length scales that are far greater than people expected. To be able to infer this, we've had to draw on data from many different fields across mineralogy, geochemistry, geophysics and sedimentology."

Keller hopes the study will spur further research. "I hope this motivates people in the different fields that it touches," he said. "I think it would be really cool if this got people talking to each other in renewed ways about how different parts of the Earth system are connected."

...

https://www.sciencedaily.com/releases/2023/05/230525140951.htm
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kassy

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Re: Earth through time
« Reply #44 on: June 01, 2023, 10:15:17 AM »
Phenomenal phytoplankton: Scientists uncover cellular process behind oxygen production

One out of 10 breaths contains oxygen generated by cellular mechanism in microscopic algae

Take a deep breath. Now take nine more. According to new research, the amount of oxygen in one of those 10 breaths was made possible thanks to a newly identified cellular mechanism that promotes photosynthesis in marine phytoplankton.

Described as "groundbreaking" by a team of researchers at UC San Diego's Scripps Institution of Oceanography, this previously unknown process accounts for between 7% to 25% of all the oxygen produced and carbon fixed in the ocean. When also considering photosynthesis occuring on land, researchers estimated that this mechanism could be responsible for generating up to 12% of the oxygen on the entire planet.

Scientists have long recognized the significance of phytoplankton -- microscopic organisms that drift in aquatic environments -- due to their ability to photosynthesize. These tiny oceanic algae form the base of the aquatic food web and are estimated to produce around 50% of the oxygen on Earth.

The new study, published May 31 in the journal Current Biology, identifies how a proton pumping enzyme (known as VHA) aids in global oxygen production and carbon fixation from phytoplankton.

"This study represents a breakthrough in our understanding of marine phytoplankton," said lead author Daniel Yee, who conducted the research while a PhD student at Scripps Oceanography and currently serves as a joint postdoctoral researcher at the European Molecular Biology Laboratory and University of Grenoble Alpes in France. "Over millions of years of evolution, these small cells in the ocean carry out minute chemical reactions, in particular to produce this mechanism that enhances photosynthesis, that shaped the trajectory of life on this planet."

...

Once the underlying mechanism was established, the team was able to connect it to multiple aspects of evolution. Diatoms were derived from a symbiotic event between a protozoan and an algae around 250 million years ago that culminated into the fusing of the two organisms into one, known as symbiogenesis. The authors highlight that the process of one cell consuming another, known as phagocytosis, is widespread in nature. Phagocytosis relies on the proton pump to digest the cell that acts as the food source. However, in the case of diatoms, something special occurred in which the cell that was eaten didn't get fully digested.

"Instead of one cell digesting the other, the acidification driven by the proton pump of the predator ended up promoting photosynthesis by the ingested prey," said Tresguerres. "Over evolutionary time, these two separate organisms fused into one, for what we now call diatoms."

Not all algae have this mechanism, so the authors think that this proton pump has given diatoms an advantage in photosynthesis. They also note that when diatoms originated 250 million years ago, there was a big increase in oxygen in the atmosphere, and the newly discovered mechanism in algae might have played a role in that.

The majority of fossil fuels extracted from the ground are believed to have originated from the transformation of biomass that sank to the ocean floor, including diatoms, over millions of years, resulting in the formation of oil reserves. The researchers are hopeful that their study can provide inspiration for biotechnological approaches to improve photosynthesis, carbon sequestration, and biodiesel production. Additionally, they think it will contribute to a better understanding of global biogeochemical cycles, ecological interactions, and the impacts of environmental fluctuations, such as climate change.

...

https://www.sciencedaily.com/releases/2023/05/230531150117.htm
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kassy

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Re: Earth through time
« Reply #45 on: June 17, 2023, 05:47:23 PM »
A Day On Earth Stalled At 19 Hours For A Billion Years, Say Scientists


Earth may currently be spinning faster, but a day on our planet lasts 24 hours largely because of the presence of the moon—and it’s gradual drift away from us.

There are other factors—including processes in the Earth’s core and solar tides related to the atmosphere heating up during daytime—but tidal forces from our moon are the most critical in determining the length of a day on Earth.

However, it appears that the length of a day on Earth hasn’t got slightly longer over deep time. There appears to have been a stalling, which may be responsible for a flourishing of plant life—and a surge in oxygen levels.

...

Not slow and steady
The study does not find a slow and steady change in day length going back in time, as most models of Earth’s rotation predict.

Most such research studies tidal mud flats preserved in sedimentary rocks—with the number of layers indicating the the number of tides, which give away the number of hours in an ancient day.

This new research uses the science of cyclostratigraphy, which uses rhythms found in vast layers of sediment to add long-term astronomical cycles to the mix. These so-called Milankovitch astronomical cycles include, according to NASA:

The shape of Earth’s orbit (its eccentricity)
The angle Earth’s axis, which is tilted with respect to Earth’s orbital plane (obliquity).
The direction Earth’s axis of rotation (precession).

...

19 hour day
Using that new data led to evidence that day length may have have stalled at a constant value in Earth’s distant past—about 19 hours—not because of the moon slowing down the planet’s rotation, but because of the sun speeding it up.

One to two billion years ago Earth rotated more quickly, which would have made the tidal pull of the moon weaker. Solar atmospheric tides would have been stronger. When they reached a certain point they could have canceled each other out. “Because of this, if in the past these two opposite forces were to have been equal to each other, such a tidal resonance would have caused Earth’s day length to stop changing and to have remained constant for some time,” said Kirscher.

Oxygen surge
One to two billion years ago is also between the times of two of the biggest surges in oxygen levels on Earth. That suggests that the length of day stalling at 19 hours for a billion years may have been instrumental in allowing plants enough time to photosynthesize and therefore thrive on Earth—and so help create lots of oxygen for in the planet’s atmosphere. “It’s fascinating to think that the evolution of the Earth’s rotation could have affected the evolving composition of the atmosphere,” said Timothy Lyons of the University California, Riverside, who was not involved in the study.

https://www.forbes.com/sites/jamiecartereurope/2023/06/15/a-day-on-earth-stalled-at-19-hours-for-a-billion-years-say-scientists/

Mid-Proterozoic day length stalled by tidal resonance

Abstract
We present statistical analysis of a compilation of observational constraints on the Precambrian length of day and find that the day length stalled at about 19 h for about 1 billion years during the mid-Proterozoic. We suggest that the accelerative torque of atmospheric thermal tides from solar energy balanced the decelerative torque of lunar oceanic tides, temporarily stabilizing Earth’s rotation. This stalling coincides with a period of relatively limited biological evolution known as the boring billion.

https://www.nature.com/articles/s41561-023-01202-6
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kassy

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Re: Earth through time
« Reply #46 on: July 19, 2023, 01:07:39 PM »
Scientists discover 36-million-year geological cycle that drives biodiversity

Movement in the Earth's tectonic plates indirectly triggers bursts of biodiversity in 36-million-year cycles by forcing sea levels to rise and fall, new research has shown.

Researchers including geoscientists at the University of Sydney believe these geologically driven cycles of sea level changes have a significant impact on the diversity of marine species, going back at least 250 million years.

As water levels rise and fall, different habitats on the continental shelves and in shallow seas expand and contract, providing opportunities for organisms to thrive or die. By studying the fossil record, the scientists have shown that these shifts trigger bursts of new life to emerge.

The research has been published in the journal Proceedings of the National Academy of Sciences, led by Associate Professor Slah Boulila from Sorbonne University in Paris.

Study co-author Professor Dietmar Müller, from the School of Geosciences at the University of Sydney, said: "In terms of tectonics, the 36-million-year cycle marks alterations between faster and slower seafloor spreading, leading to cyclical depth changes in ocean basins and in the tectonic transfer of water into the deep Earth.

"These in turn have led to fluctuations in the flooding and drying up of continents, with periods of extensive shallow seas fostering biodiversity.

"This work was enabled by the GPlates plate tectonic software, developed by the EarthByte Group at the University of Sydney, supported by Australia's National Collaborative Research Infrastructure Strategy (NCRIS) via AuScope."

The team based their findings on the discovery of strikingly similar cycles in sea-level variations, Earth's interior mechanisms and marine fossil records.

Scientists now have overwhelming evidence that tectonic cycles and global sea level change driven by Earth's dynamics have played a crucial role in shaping the biodiversity of marine life over millions of years.

"This research challenges previous ideas about why species have changed over long periods," Professor Müller said.

"The cycles are 36 million years long because of regular patterns in how tectonic plates are recycled into the convecting mantle, the mobile part of the deep Earth, similar to hot, thick soup in a pot, that moves slowly."

Professor Müller said the Cretaceous Winton Formation in Queensland serves as a prime example of how sea-level changes have shaped ecosystems and influenced biodiversity in Australia.

The formation, renowned for its collection of dinosaur fossils and precious opal, provides a valuable window into a time when much of the Australian continent was flooded.

As sea levels rose and fell, the flooding of the continent created expanding and contracting ecological recesses in shallow seas, providing unique habitats for a wide range of species.

"The Cretaceous Winton Formation stands as a testament to the profound impact of these sea-level changes, capturing a snapshot of a time when Australia's landscape was transformed and fascinating creatures roamed the land," Professor Müller said.

https://www.sciencedaily.com/releases/2023/07/230710180454.htm
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trm1958

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Re: Earth through time
« Reply #47 on: July 20, 2023, 03:53:21 PM »

Or for an even longer timeline:

This one doesn't go as far back, but it goes 250 My ahead:
« Last Edit: July 20, 2023, 03:59:55 PM by trm1958 »

morganism

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Re: Earth through time
« Reply #48 on: August 09, 2023, 12:21:56 AM »

kassy

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Re: Earth through time
« Reply #49 on: August 17, 2023, 11:50:37 PM »
Evidence of Earth’s Oldest Glaciers Found in South Africa


Earth may have hosted glaciers as far back as 3 billion years ago, reports a new study published in Geochemical Perspectives Letters. Drawing on multiple lines of evidence from some of the oldest undisturbed rocks on Earth, the study authors said they see evidence for ice sheets during the planet’s ancient Archaean eon similar to those found today in mountain ranges across the world. It is the oldest evidence of glaciers ever discovered.

Signs of these ancient glaciers come from a region called the Pongola Supergroup, which underlies parts of South Africa. There, mining companies drilled boreholes to retrieve rock samples more than 3 kilometers down. Some of these rocks, in addition to others found at the surface, formed around 3 billion years ago and reveal geological features similar to those found in glacial moraines today: chaotically jumbled rocks, finely ground sediments, and even rare dropstones, which melted through the ice.

As far back as the 1990s, researchers proposed that the features in South Africa suggested the presence of ancient glaciers, though their claims were not widely supported. The conditions of the planet’s climate during the Archaean have been debated for decades. Earth’s interior was hotter than it is today, but the Sun’s light was weaker, making it unclear whether our planet was hotter, colder, or about the same as it is today.

With a new line of evidence made possible by more modern techniques, two researchers argue they’ve found proof of glaciers during the Archaean in the Pongola samples, shedding more light on our planet’s early climate. Applying a technique known as triple oxygen isotope analysis revealed strong evidence of near-freezing-cold water interacting with the rocks at that time, said Ilya Bindeman, a stable isotope geochemist at the University of Oregon and study coauthor. That water would likely have melted out of the glaciers, according to Bindeman.

Revealing Ancient Ice
Oxygen comes in three stable isotopes: oxygen-16, oxygen-17, and oxygen-18. Oxygen-17 and -18 are heavier than oxygen-16 because they contain more neutrons. Water molecules containing those isotopes tend to get left behind when water evaporates from the oceans. So clouds, and the rain they create, contain relatively more oxygen-16 than the oceans. The heavier oxygen isotopes that do make it into clouds also fall out as rain more quickly than oxygen-16.

Colder temperatures and low humidity cause precipitation to form that’s relatively rich in the heaviest isotope—oxygen-18—leaving the leftover water vapor enriched in the lighter oxygen. As temperatures fall, precipitation becomes increasingly rich in oxygen-16 compared to oxygen-18, making low levels of oxygen-18 a good proxy for cold temperatures.

Using a mass spectrometer, Bindeman and coauthor Axel Hofmann, a geologist at the University of Johannesburg in South Africa, measured the ratios of oxygen isotopes in shales and diamictites from samples taken from the Pongola Supergroup dated to 2.9 billion years old. These minerals formed when water interacted with existing rocks, causing reactions that chemically bound oxygen into the rocks.

Analyzing those oxygen atoms 3 billion years later, the researchers found levels of oxygen-18 that are as much as 2.8% lower than those found in standard ocean water, indicating the rocks interacted with water that formed in cold conditions, like that found melting from ice. Together with the existing signs of glacial moraines found in the rock strata, the oxygen data are evidence of glaciers during the Archaean.

and more:
https://eos.org/articles/evidence-of-earths-oldest-glaciers-found-in-south-africa

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