Earth through time

[kassy]

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

[kassy]

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.

[Freegrass]

....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...

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/

[squilliam]

@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]

The whole explanation is in modelling them at their own proper size which is a nice elegant solution.

[Sigmetnow]

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

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

[kassy]

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. 

[kassy]

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.

[kassy]

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.

[kassy]

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.

[kassy]

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

[kassy]

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

[kassy]

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/

[Tor Bejnar]

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).

[Sigmetnow]

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

[Tor Bejnar]

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

[kassy]

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.

[kassy]

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

[kassy]

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

[kassy]

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

[Freegrass]

Earth is just a little blip in time...

[kassy]

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.

[kassy]

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...

[Laurent]

You can acces some data from here : http://portal.gplates.org/cesium/?view=rift_v&utm_campaign=buffer

or here https://dinosaurpictures.org/ancient-earth#35

[kassy]

Thanks Laurent, those are some really cool links to play with! They give nice control over time and you can drag the planet around.

[kassy]

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

[kassy]

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.

[kassy]

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

[kassy]

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

[kassy]

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

[kassy]

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/

[kassy]

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

[kassy]

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

[kassy]

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