Geology, Earthquakes & Volcanism News and Discussions

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caltrek
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Geologists Have Closely Analyzed Two Bizarre 'Blobs' Detected Deep Inside Earth
by Carly Cassella
March 11, 2022

https://www.sciencealert.com/two-weird- ... -different

Introduction:
(Science Alert) 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.
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Magnitude 7.3 earthquake hits northern Japan, triggering tsunami alerts

23 mins ago

A magnitude 7.3 earthquake was recorded off the coast of Fukushima and Miyagi, Japan, on Wednesday, tripping tsunami alerts in the northeastern regions, according to the country's meteorological agency.

The big picture: The earthquake struck just days after the 11th anniversary of the 9.0 magnitude earthquake and tsunami that devastated Fukushima and triggered a nuclear crisis.

https://www.axios.com/earthquake-japan- ... 9ed5a.html


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caltrek
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This Could Be Why the Massive Volcanic Eruption in Tonga Was So Explosive
by David Nield
March 31, 2022

https://www.sciencealert.com/this-could ... -explosive

Introduction:
(Science Alert) By any measure you want to use, the Hunga Tonga-Hunga Ha'apai volcano eruption in January 2022 was a massive eruption.

It produced a swirling plume of gas, dust and ash that reached 58 kilometers (36 miles) into the sky, atmospheric waves that traveled around the globe several times, and tsunamis in the Caribbean on the other side of the world.

A newly published study now suggests why the scale of this volcanic blast was so huge: a smaller eruption the day before, priming the volcano for a bigger explosion by sinking its main vent under the surface of the ocean.

That meant molten rock was spewing out straight into seawater, vaporizing it along the way and intensifying the eruption. The vaporizing seawater caused the lava to fragment into tiny bits of ash, the researchers suggest.

Combined with ice crystals in the upper atmosphere, the roiling cloud of material built static charges that drove a dramatic period of lightning. The frenzy of electrical activity was so intense, in fact, it represented 80 percent of Earth's lightning strikes in its most active hour.
The research paper is available at this link: https://www.sciencedirect.com/science/a ... 7022000227
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Largest earthquake in history happened in Chile 3,800 years ago, study finds

Yikes... if something like this were to play out today...

https://www.ctvnews.ca/sci-tech/largest ... -1.5867024
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Deep Lake Cores of Ancient Lake Cahuilla Could Help Define Southern San Andreas Fault History
April 22, 2022

https://www.eurekalert.org/news-releases/950625

Introduction:
(EurekAlert) Sediment cores from the ancient Lake Cahuilla at Coachella in southern California could help seismologists determine whether lake filling events are connected to earthquakes on the Southern San Andreas Fault, according to a presentation at the Seismological Society of America’s Annual Meeting.

Lake Cahuilla was a prehistoric lake in California and northern Mexico that covered more than 2000 square miles in the Coachella and Imperial valleys, in the same region as the Southern San Andreas Fault. Today’s Salton Sea occupies part of the original lake footprint.

Sediment layers in two cores, dated with a technique called single-grain luminescence, now extend the lake level history back to about 7000 years, from the previous record of about 2000 years, said Sourav Saha of the Kentucky Geological Survey, University of Kentucky.

Recent paleoseismology studies along the Southern San Andreas Fault suggest that the last seven major ruptures on the fault have occurred at intervals between 116 to 221 years. However, the most recent earthquake in the Lake Cahuilla region occurred about 300 years ago, at the last time the lake was filled. “One of our goals is to see whether there is any relationship between fluctuations in the lake and the activation of the Southern San Andreas Fault,” Saha said.

Some geophysicists think that past fault ruptures might be linked to stages of lake filling, he explained. The increase in pore pressure that could result from lake filling “would most likely reactivate smaller normal faults along the Salton Sea stepover zone, and Coulomb stress models indicate that if you reactivate those extensional faults, it is very likely that you don’t need much to reactivate the Southern San Andreas Fault.”
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What Can Deep Diamonds Tell Us About Deep Earthquakes?
April 22, 2022

https://www.eurekalert.org/news-releases/950624

Introduction:
(EurekAlert) Diamonds that formed deep in the Earth could help seismologists answer a decades-old question: do fluids play a role in generating earthquakes at depths where high pressure should keep brittle failure from happening?

Fluid-assisted faulting in subducted slabs 300 to 700 kilometers deep, in the transition zone between upper and lower mantle, is one process that might explain deep earthquakes. But good evidence for water or other fluids associated with these slabs based on samples was scarce until recently, according to Steven Shirey of the Carnegie Institution for Science.

Now, studies of diamonds that formed in the transition zone provide evidence of fluids carried by subducted slabs. Along with new subduction zone modeling, these diamonds make it clear that fluids can’t be ignored in the story of deep earthquake generation, Shirey said at the Seismological Society of America’s Annual Meeting.

Not all deep earthquakes have to involve water, but modeling by Shirey and his colleagues suggests that some subducting slabs remain cold enough to hold on to and transport water all the way to the bottom of the transition zone. Deep earthquakes, occurring 500 to 700 kilometers below the Earth’s surface, seem to only happen in these slabs that can transport water or that can carry carbonate deep enough to trigger melting, they found.

At that depth, water or carbonate fluids could be triggering the earthquakes, or the earthquakes could be triggering fluid release—or both things could be happening, Shirey said.
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Tonga eruption was 'record atmospheric explosion'

17 minutes ago

The eruption of the Tonga volcano in January has been confirmed as the biggest explosion ever recorded in the atmosphere by modern instrumentation.

It was far bigger than any 20th Century volcanic event, or indeed any atom bomb test conducted after WWII.

The assessment comes in a pair of scholarly papers in the journal Science that have reviewed all the data.

Of recent history, it's likely only the Krakatoa eruption of 1883 rivalled the atmospheric disturbance produced.

That catastrophic event in Indonesia is thought to have claimed more than 30,000 lives. Fortunately, the 15 January climactic eruption of the underwater volcano at Hunga Tonga-Hunga Ha'apai (HTHH) in the south Pacific resulted in very few deaths, even though it too produced large tsunamis.

https://www.bbc.co.uk/news/science-environment-61452860
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caltrek
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While this article (see below) is slightly dated, it was recently cited by Erowind in the chat room, and I do not recall seeing it in this forum before.

Study Confirms that Tonga Volcano Eruption Unlikely to Cool Earth
by Elizabeth Howell
March 01, 2022
(Space.com) The Hunga Tonga volcanic eruption that shook the South Pacific Ocean in January will not affect Earth's climate despite sending clouds of ash dozens of miles high into the atmosphere, a new study confirmed.

Powerful volcanic eruptions, such as the one that ripped apart the uninhabited Polynesian island of Hunga Tonga-Hunga Ha'apai on Jan. 15, sometimes cause short-term cooling of the planet. But this won't be the case of the recent mega-eruption, in spite of the fact that it spewed volcanic ash into record altitudes of more than 25 miles (40 kilometers).

The new study confirms previous estimates, stating that the cooling effect of Hunga Tonga could range from just 0.014 degrees Fahrenheit (0.004 degrees Celsius) in the northern hemisphere and up to 0.018 degrees F (0.01 degrees C) in the southern hemisphere, which is even less than some of the previous estimates expected.
Read more here: https://www.space.com/tonga-volcano-eru ... prediction
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