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vox_mundi

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Re: Volcanoes
« Reply #150 on: October 17, 2019, 08:41:46 PM »
Underwater Volcano Creates Bubbles More Than a Quarter-Mile Across
https://www.livescience.com/amp/giant-bubbles-underwater-volcano.html

In the early 20th century, sailors near Alaska reported seeing black bubbles seeming to boil out from the sea, each one the size of the dome of the capitol building in Washington, D.C. They weren't the only sailors who reported the bizarre phenomenon, and they weren't mistaken, except for one thing … the bubbles were much larger.

When the mostly underwater Bogoslof volcano in the Aleutian Islands erupts, it produces giant bubbles that can reach up to 1,444 feet (440 meters) across, according to a new study. These bubbles are filled with volcanic gas, so when they burst they create volcanic clouds tens of thousands of feet in the sky, said lead author John Lyons, a research geophysicist at the Alaska Volcano Observatory of the U.S. Geological Survey.

... "These shallow explosive submarine eruptions are so rare," Lyons said. "There's a lot of undersea volcanism, but the majority of it happens under lots and lots of water very deep and all that extra pressure tends to suppress how explosive eruptions are."

Lyons, et.al Infrasound from giant bubbles during explosive submarine eruptions, Nature Geoscience 2019
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late

vox_mundi

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Re: Volcanoes
« Reply #151 on: December 09, 2019, 06:22:13 PM »
Five Dead, Many Missing and ‘No Signs of Life’ After Volcanic Eruption on New Zealand Island
https://www.washingtonpost.com/nation/2019/12/08/white-island-whakaari-eruption-new-zealand-jacinda-ardern/

At least five people are dead with many others reported missing — and authorities fearing the worst — after a volcano erupted Monday at a popular tourist site in New Zealand.

Several dozen visitors, including some from a Royal Caribbean cruise ship, were on or near White Island when it erupted at 2:11 p.m. local time, releasing thick clouds of ash about 12,000 feet into the air. Some 18 people suffered serious burn injuries and were rescued.

Police do not believe there are any survivors among the missing, following what scientists called a “throat-clearing kind of eruption.”

“No signs of life have been seen at any point,” New Zealand Police said in a statement. “Police believe that anyone who could have been taken from the island alive was rescued at the time of the evacuation. Based on the information we have, we do not believe there are any survivors on the island.”

Deputy Commissioner John Tims said at a news conference that he didn’t know how many are still unaccounted for, estimating that figure to be in the “double digits.”



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Volcano F is Origin of 'Floating Stones'
https://phys.org/news/2019-12-volcano-stones.html


Stones do not float in water—this is a truism. But there is hardly a rule without exception. In fact, some volcanic eruptions produce a very porous type of rock with a density so low that it does float: Pumice. An unusually large amount of it is currently drifting in the Southwest Pacific towards Australia. When it was first sighted in the waters around the island state of Tonga at the beginning of August, it almost formed a coherent layer on the ocean's surface. The "pumice raft" made it into headlines all over the world.

Various underwater volcanoes were discussed at that time as the potential source. But direct proof for the exact origin of the pumice was missing so far. Researchers at the GEOMAR Helmholtz Centre for Ocean Research Kiel (Germany), together with colleagues from Canada and Australia, are now publishing evidence in the Journal of Volcanology and Geothermal Research that clearly identifies the culprit. It is a so far nameless underwater volcano just 50 kilometres northwest of the Tongan island of Vava'u. "In the international scientific literature, it appears so far only under the number 243091 or as Volcano F," says Dr. Philipp Brandl of GEOMAR, first author of the study.

... The team found what they were looking for on of freely accessible satellite images. On an image of the ESA satellite Copernicus Sentinel-2 taken on 6 August 2019, clear traces of an active underwater eruption can be seen on the water surface. Since the images are exactly georeferenced, they could be compared with corresponding bathymetric maps of the seafloor. "The eruption traces fit exactly to Volcano F," says Dr. Brandl.

“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late

Rodius

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Re: Volcanoes
« Reply #152 on: December 10, 2019, 02:03:58 AM »
White Island, the very active volcano that became more active and killed some people this week, is always dangerous to visit.
I have watched it explode a few times and it is called White Island because it is almost always active.

I am surprised that people are allowed to visit it as often as they do.

Anyway, this event was never an "if" event.... it is a "when" event. Tourists are warned about the dangers and decide to go anyway (because bad things only happen to other people).

While it is sad that people have died, and maybe I am a cold-hearted person, but I don't feel sorry for the situation given they visit with eyes wide open.

There is plenty of geological activity 100km +/- inland in Rotorua that is actually much, much safer.

Edit: I forgot to mention that there is now a reasonable chance of an earthquake there now.
« Last Edit: December 10, 2019, 02:22:05 AM by Rodius »

KiwiGriff

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Re: Volcanoes
« Reply #153 on: December 10, 2019, 03:37:51 AM »
I would not say any of our active volcanoes are  ever 100% safe.
Any  of them could have an eruption at any time . Even our biggest city is built on a massive volcanic field that has historically had an eruption every 500 years. last eruption in Auckland,  rangitoto, was 600 years ago .
The warning level on White island was at three but there is plenty of occasions when the volcanoes are at elevated risk and nothing happens. It is dangerous to walk around on an active volcano that is part of the attraction. Shite happens I am sorry that some died but ffs don't make it impossible to experience earths wonders because the natural world also comes complete with some risk.

I have a pet rock that jumped onto my boat 500 Nautical miles out in the pacific  :D
Seeing a raft of pumice that goes on for days is an awesome sight
I sailed though the one from the Home Reef eruption  in 2006.

Edit alert level was at two.
« Last Edit: December 10, 2019, 11:34:21 AM by KiwiGriff »

Rodius

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Re: Volcanoes
« Reply #154 on: December 10, 2019, 08:26:55 AM »
I would not say any of our active volcanoes are  ever 100% safe.
Any  of them could have an eruption at any time . Even our biggest city is built on a massive volcanic field that has historically had an eruption every 500 years. last eruption in Auckland,  rangitoto, was 600 years ago .
The warning level on White island was at three but there is plenty of occasions when the volcanoes are at elevated risk and nothing happens. It is dangerous to walk around on an active volcano that is part of the attraction. Shite happens I am sorry that some died but ffs don't make it impossible to experience earths wonders because the natural world also comes complete with some risk.

I have a pet rock that jumped onto my boat 500 Nautical miles out in the pacific  :D
Seeing a raft of pumice that goes on for days is an awesome sight
I sailed though the one from the Home Reef eruption  in 2006.

I personally wouldnt go on White Island.... but I agree, some things are worth the risk and each evaluates their own levels. I mean, for me, I have climbed Tongariro twice and that blows up sometimes. It actually did it once 2 weeks after I climbed it lol.
The Southern Alps were my hiking paradise for a decade, I even got horribly lost there once because I underestimated the risk.
I have sat beside wild lions with nothing but fresh air between us.

Hmmmm, maybe I should visit White Island one day. But if it blows up, I wouldnt go around saying " I cant believe it blew up"


Tor Bejnar

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Re: Volcanoes
« Reply #155 on: December 10, 2019, 03:46:20 PM »
VOLCANO NEWS (http://www.sveurop.org/gb/news/news.htm) carries brief reports from many volcanoes around the world.  Some are updated more frequently than others.

Quote
NEW ZEALAND - White island volcano

December 10th, 2019

GEONET reported that since December 10th in the morning, seismic activity has remained low, but periodic jets of steam are still continuing and gas from the active ventilation zone. The volcanic alert level remains at level 3. The aviation color code remains orange. Over the next 24 hours, scientists will still estimating an equal probability of no eruption or a smaller / similar size eruption that would impact the floor of the main crater, based on our observations and measurements. GEONET reported that a phreatic eruption occurred on December 9 around 14:11 local time on White Island in northern New Zealand. This short-lived impulsive event affected the bottom of the crater. Activity seems to have decreased since the eruption. Monitoring data shows that there was a short-lived eruption that generated an ash plume at about 3,600 meters above the vent. Ashes covered the floor of the main crater, where there were about fifty people. ...
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johnm33

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Re: Volcanoes
« Reply #156 on: December 10, 2019, 05:21:59 PM »
Lightning strikes  change the time to the 8th and apply, suggests when not to visit.

KiwiGriff

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Re: Volcanoes
« Reply #157 on: December 10, 2019, 07:00:42 PM »
Quote
Whakaari/White Island has been at a level two alert level 10 times since 2012, but yesterday was the first time it went from level two to an eruption.

While tour operators felt this level was within operating guidelines, some experts say the eruption wasn't wholly unexpected and even a "disaster waiting to happen".

Data gained from GeoNet website bulletins shows the alert level has reached two twice this year. It also reached the level in 2016, 2013 and 2012.

The bulletins show that yesterday's eruption was the first time an alert level of two led to an eruption. Eruptions in 2016 occurred when the alert level was at one.
https://www.stuff.co.nz/national/118101001/whakaari--white-island-a-level-two-sense-of-security

Web site for NZ geological hazards monitoring .
https://www.geonet.org.nz/

vox_mundi

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Re: Volcanoes
« Reply #158 on: December 18, 2019, 06:50:07 PM »
Undersea Volcanism May Explain Medieval Year of Darkness
https://phys.org/news/2019-12-undersea-volcanism-medieval-year-darkness.html
https://blogs.ei.columbia.edu/2019/12/17/undersea-volcanism-medieval-darkness/

Starting in 536 A.D., the sky went dark for more than a year. In some parts of Europe and Asia, the sun only shone for about four hours a day, and "accounts say the sun gave no more light than the moon," says Dallas Abbott, who studies paleoclimate and extraterrestrial impacts at Columbia University's Lamont-Doherty Earth Observatory. The mysterious dimming of the sun brought on global cooling, famines, and civil upheavals; the Chinese reported eclipses that still can't be explained today. Trees struggled to grow from 536 to 555 A.D., suggesting that the solar dimming was extensive, and scholars don't know exactly why.

Last week, in a poster at the meeting of the American Geophysical Union, Abbott and her colleague John Barron from the U.S. Geological Survey presented a new interpretation of the event.

Volcanic eruptions have been known spew sulfur and other particles into the atmosphere that can block out sunlight. But geological records only indicate big eruptions in 536 and 541, which aren't enough to explain the nine-year downward spike in tree growth. In addition, it would require a lot of sulfur and ash to darken the sky so much, and some of that material should be visible in rock layers and ice cores. However, says Abbott, "the amount of sulfate that was deposited wasn't as much as in other eruptions where they experience a similar amount of dimming."

That led her and Barron to suspect that perhaps impacts from space rocks could have thrown up enough dust to cause the dimming. But now, after analyzing a Greenland ice core, they have another theory.

Surprisingly, the layers of the ice core contained 91 fossils of microscopic species that would have lived in warm, tropical waters. "We found by far the most low-latitude microfossils that anybody's ever found in an ice core," says Abbott. By comparison, they were only able to identify one high-latitude species in the mix.

How did all those warmth-loving tropical and subtropical species get all the way up onto the Greenland ice sheet?

The team suspects they were blown into the atmosphere by underwater volcanic eruptions near the equator. Rather than emitting lots of sulfur, these submarine eruptions (in approximately 536 and 538 A.D.) would have vaporized seawater, the rising steam carrying calcium-laden sediments and microscopic sea creatures into the atmosphere. After floating around the atmosphere for a while, some of these particles would have eventually settled in the Arctic.

Equatorial volcanic eruptions in particular can affect the entire globe and, once in the atmosphere, the white sediments and microorganisms would have been very good at reflecting sunlight back into space. They're also difficult to detect in sediment records, which explains why they hadn't been noticed before.



Researchers discovered a high number of fossils from tropical areas (blue line) deposited in the Greenland ice during the 6th century. This indicates that underwater eruptions near the equator may have contributed to epic sky-dimming during 536-537 A.D. (The black line shows sulfate levels in the ice core, an indicator of another type of volcanic eruption.)

Background:

https://www.nature.com/news/2008/080311/full/news.2008.665.html

https://link.springer.com/article/10.1007/s10584-016-1648-7


Surface temperature anomalies simulated by the MPI-ESM in response to the reconstructed volcanic forcing for the 536 and 540 eruptions. (a) Timeseries of simulated Northern Hemisphere mean monthly mean surface temperature anomalies: individual ensemble members shown in light blue, ensemble mean in thick blue. Gray shading shows the ±2σ variability of the control run, dashed grey lines show the ±4σ and ±8σ variability levels. Global maps of the simulated 536–545 CE decadal mean boreal (b) summer and (c) winter mean temperature anomalies
« Last Edit: December 18, 2019, 07:23:52 PM by vox_mundi »
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late

vox_mundi

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Re: Volcanoes
« Reply #159 on: December 29, 2019, 08:32:37 PM »
Forces from Earth's Spin May Spark Earthquakes and Volcanic Eruptions
https://phys.org/news/2019-12-earth-earthquakes-volcanic-eruptions-mount.html



New research suggests forces pulling on Earth's surface as the planet spins may trigger earthquakes and eruptions at volcanoes

Seismic activity and bursts of magma near Italy's Mount Etna increased when Earth's rotational axis was furthest from its geographic axis, according to a new study comparing changes in Earth's rotation to activity at the well-known Italian volcano.

Earth's spin doesn't always line up perfectly with its north and south poles. Instead, the geographic poles often twirl like a top around Earth's rotational axis when viewed from space. Every 6.4 years, the axes line up and the wobble fades for a short time—until the geographic poles move away from the spin axis and begin to spiral once again.

This phenomenon, called polar motion, is driven by changes in climate due to things like changing seasons, melting ice sheets or movement from tectonic plates. As polar motion fluctuates, forces pulling the planet away from the sun tug at Earth's crust, much like tides due to the gravitational pull from the sun and moon. The tide from polar motion causes the crust to deform over the span of seasons or years. This distortion is strongest at 45 degrees latitude, where the crust moves by about 1 centimeter (0.4 inches) per year.

Now, a new study published in AGU's journal Geophysical Research Letters suggests that polar motion and subsequent shifts in Earth's crust may increase volcanic activity.

... Lambert and Sottili discovered there were more earthquakes when Earth's rotational pole was furthest from the geographic axis—at the point in Earth's top-like spin when it looks like it is about to fall over. Between 1999 and 2019, those peaks were in 2002 and 2009. An expected peak in 2015 never materialized because one of the oscillations contributing to polar motion has been slowing down.



S. Lambert et al. Is there an influence of the pole tide on volcanism? Insights from Mount Etna recent activity, Geophysical Research Letters (2019)
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late

vox_mundi

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Re: Volcanoes
« Reply #160 on: January 06, 2020, 05:43:57 PM »
Formation of a Huge Underwater Volcano Offshore the Comoros
https://phys.org/news/2020-01-formation-huge-underwater-volcano-offshore.html

A new submarine volcano was formed off the island of Mayotte in the Indian Ocean in 2018. This was shown by an oceanographic campaign in May 2019. Now, an international team led by the scientist Simone Cesca from the German GeoForschungsZentrum GFZ is illuminating the processes deep inside the Earth before and during the formation of the new volcano. It is akin to detecting a new type of signal from the Earth's interior that indicates a dramatic movement of molten rocks before the eruption. With their specially developed seismological methods, the researchers are reconstructing the partial emptying of one of the deepest and largest active magma reservoirs ever discovered in the upper mantle. The study is published in the journal Nature Geoscience.

... "It is the deepest (~30 km) and largest magma reservoir in the upper mantle (more than 3.4 cubic kilometers) to date, which is beginning to empty abruptly.

"Since the seabed lies 3 kilometers below the water surface, almost nobody noticed the enormous eruption. However, there are still possible hazards for the island of Mayotte today, as the Earth's crust above the deep reservoir could continue to collapse, triggering stronger earthquakes," says Torsten Dahm, head of the section Physics of Earthquakes and Volcanoes at the GFZ.



Drainage of a deep magma reservoir near Mayotte inferred from seismicity and deformation, Nature Geoscience (2020)
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late