Tag Archive: Geological Society of America


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Eaten away by ‘vog’: Acid fog eroding rocks on Mars

The planet Mars showing showing Terra Meridiani is seen in an undated NASA image. © Greg Shirah
Scientists believe they have figured out why rocks on Mars are eroding. They say an acidic fog created by volcanic eruptions on the red planet is the probable culprit.

Planetary scientist Shoshanna Cole came up with the theory after studying a 100-acre area on Husband Hill in the Columbia Hills of the Gusev Crater on Mars using data gathered by a number of instruments on the 2003 Mars Exploration Rover Spirit.

She found that acidic vapors released by eruptions may have been responsible for eating away rocks on the Watchtower Class outcrops on the Cumberland Ridge and Husband Hill summit.

View image on Twitter

Acid fog corroded the surface of Mars: a new discovery from NASA’s long-dead Spirit rover. http://bit.ly/1H6jT0V 

“The special thing about Watchtower Class is that it’s very widespread and we see it in different locations. As far as we can tell, it is part of the ground there,” which means that these rocks record environments that existed on Mars billions of years ago, Cole said in a press release submitted by the Geological Society of America.

 

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Geophysicists have imaged the magma chambers that blew the lid off Mount St. Helens in its 1980 eruption.

Dean J. Koepfler/MCT/Newscom

Geophysicists have imaged the magma chambers that blew the lid off Mount St. Helens in its 1980 eruption.

Deep magma chambers seen beneath Mount St. Helens

Geoscientists have for the first time revealed the magma plumbing beneath Mount St. Helens, the most active volcano in the Pacific Northwest. The emerging picture includes a giant magma chamber, between 5 and 12 kilometers below the surface, and a second, even larger one, between 12 and 40 kilometers below the surface. The two chambers appear to be connected in a way that could help explain the sequence of events in the 1980 eruption that blew the lid off Mount St. Helens.

So far the researchers only have a two-dimensional picture of the deep chamber. But if they find it extends to the north or south, that would imply that the regional volcanic hazard is more distributed rather than discrete, says Alan Levander, a geophysicist at Rice University in Houston, Texas, and a leader of the experiment that is doing the subterranean imaging. “It isn’t a stretch to say that there’s something down there feeding everything,” he adds.

Levander unveiled the results on 3 November at a meeting of the Geological Society of America in Baltimore, Maryland—the first detailed images from the largest-ever campaign to understand the guts of a volcano with geophysical methods. The campaign, “imaging magma under St. Helens” (iMUSH), started in 2014 when researchers stuck 2500 seismometers in the ground on trails and logging roads around the volcano. They then detonated 23 explosive shots, each with the force of a small earthquake. “You’d feel this enormous roll in the ground, and everyone would go, ‘Oh wow’,” Levander says.

 

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2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 181-7
Presentation Time: 9:35 AM

IMUSH: MAGMA RESERVOIRS FROM THE UPPER CRUST TO THE MOHO INFERRED FROM HIGH-RESOLUTION VP AND VS TOMOGRAPHY BENEATH MOUNT ST. HELENS

KISER, Eric1, LEVANDER, Alan2, PALOMERAS, Immaculada1, ZELT, Colin A.1, SCHMANDT, Brandon3, HANSEN, Steven3, HARDER, Steven4, CREAGER, Kenneth5 and VIDALE, John E.5, (1)Earth Science, Rice University, 6100 Main Street, Houston, TX 77005, (2)Earth Science, Rice University, 6100 Main Street MS-126, Houston, TX 77005, (3)Earth & Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, (4)Dept. of Geological Sciences, University of Texas at El Paso, 500 W. University Ave., El Paso, TX 79968, (5)Earth & Space Sciences, University of Washington, Johnson Hall Rm-070 Box 351310, 4000 15th Avenue NE, Seattle, WA 98195, alan@rice.edu
Seismic investigations following the 1980 eruption of Mount St. Helens have led to a detailed model of the magmatic and tectonic structure directly beneath the volcano. These studies suffer from limited resolution below ~10 km, making it difficult to estimate the volume of the shallow magma reservoir beneath the volcano, the regions of magma entry into the lower crust, and the connectivity of this magma system throughout the crust. The latter is particularly interesting as one interpretation of the Southern Washington Cascades Conductor (SWCC) suggests that the Mount St Helens and Mount Adams volcanic systems are connected in the crust (Hill et al., 2009).

 

The multi-disciplinary iMUSH (imaging Magma Under St. Helens) project is designed to investigate these and other fundamental questions associated with Mount St. Helens. Here we present the first high-resolution 2D Vp and Vs models derived from travel-time data from the iMUSH 3D active-source seismic experiment. Significant lateral heterogeneity exists in both the Vp and Vs models. Directly beneath Mount St. Helens we observe a high Vp/Vs body, inferred to be the upper/middle crustal magma reservoir, between 4 and 13 km depth. Southeast of this body is a low Vp column extending from the Moho to approximately 15 km depth. A cluster of low frequency events, typically associated with injection of magma, occurs at the northwestern boundary of this low Vp column. Much of the recorded seismicity between the shallow high Vp/Vs body and deep low Vp column took place in the months preceding and hours following the May 18, 1980 eruption. This may indicate a transient migration of magma between these two reservoirs associated with this eruption.

 

Outside of the inferred magma bodies that feed Mount St. Helens, we observe several other interesting velocity anomalies. In the lower crust, high Vp features bound the low Vp column. One explanation for these features is the presence of lower crustal cumulates associated with Tertiary ancestral Cascade volcanism. West of Mount St. Helens, high Vp/Vs regions in the upper and middle crust have eastern boundaries that are close to the eastern boundaries of the accreted Siletzia terrain inferred from magnetic data. Finally, a low Vp channel northeast of Mount St. Helens between 14 and 18 km depth correlates well with the location of the SWCC.

 

Its scarred and jagged crater is a reminder of the terrible devastation that Mount St Helens wrought over the Washington countryside 35 years ago.

Now a new study of the volcanic plumbing lurking beneath the 8,363ft (2,459 metre) summit suggests the volcano could yet again blow its top in an explosive eruption.

Geologists studying the volcano, which is responsible for the most deadly eruption in US history, have discovered a second enormous magma chamber buried far beneath the surface.

The IMUSH project has detected signs that a second larger magma chamber may lie beneath Mount St Helens, filling the chamber directly under the volcano from below (illustrated) through a series of earthquakes. The chamber may also connect Mount St Helens to other nearby volcanoes 

The IMUSH project has detected signs that a second larger magma chamber may lie beneath Mount St Helens, filling the chamber directly under the volcano from below (illustrated) through a series of earthquakes. The chamber may also connect Mount St Helens to other nearby volcanoes

 

 

 

 

First Posted: Apr 18, 2013 04:07 PM EDT

 

Yellowstone

When volcanoes erupt, silica-rich magma can burst through the Earth’s crust, burning the surrounding area in a massive explosion. Now, it turns out that this magma can lurk in Earth’s upper crust for hundreds of thousands of years without triggering an eruption. (Photo : Flickr/Don Graham)

 

Yellowstone has the world’s largest collection of geysers, and it has the underground plumbing to prove it. Scientists have announced that the volcanic activity beneath the National Park’s surface may be far bigger and better connected than once thought.

 

The National Park is home to hot springs, mudpots, fumaroles and geysers, so it’s not surprising that it has quite a bit of volcanic activity under the ground. Known as a hotspot, a massive volume of molten magma is located beneath Yellowstone. This plume of superheated rock rises from Earth’s mantle, punching through the continent’s crust as North America has slowly drifted over it. The phenomenon has left a trail of calderas created by massive volcanic eruptions in its wake; the most recent occurred about 640,000 years ago.

 

Yellowstone is infamous for its potential for a “super eruption.” When the Huckleberry Ridge eruption in Yellowstone occurred about 2 million years ago, it darkened the skies with ash from southern California to the Mississippi River. It was one of the largest eruptions to have occurred on our planet. Understanding the volcanic activity of this location is therefore crucial for predicting future eruptions.

 

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nature.com

 

Large magma reservoir gets bigger

 

But earthquakes, not eruptions, are Yellowstone’s most serious geological risk.

 

 

28 October 2013

 

 

 

The reservoir of molten rock underneath Yellowstone National Park in the United States is at least two and a half times larger than previously thought. Despite this, the scientists who came up with this latest estimate say that the highest risk in the iconic park is not a volcanic eruption but a huge earthquake.

 

Yellowstone is famous for having a ‘hot spot’ of molten rock that rises from deep within the planet, fuelling the park’s geysers and hot springs1. Most of the magma resides in a partially molten blob a few kilometres beneath Earth’s surface.

 

New pictures of this plumbing system show that the reservoir is about 80 kilometres long and 20 kilometres wide, says Robert Smith, a geophysicist at the University of Utah in Salt Lake City. “I don’t know of any other magma body that’s been imaged that’s that big,” he says.

 

Smith reported the finding on 27 October at the annual meeting of the Geological Society of America in Denver, Colorado.

 

Yellowstone lies in the western United States, where the mountain states of Wyoming, Montana and Idaho converge. The heart of the park is a caldera — a giant collapsed pit left behind by the last of three huge volcanic eruptions in the past 2.1 million years.

 

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 Earth Watch Report

 

 

East Coast faces variety of tsunami threats

The most likely source for an East Coast tsunami would be an underwater avalanche along the continental slope.

By Douglas Main, OurAmazingPlanet Staff Writer
tsunami evacuation route sign
An offshore earthquake of magnitude 4.5 or above could cause submarine avalanches and create dangerous tsunamis with waves higher than 26 feet. (Photo: epugachev/flickr)
An offshore earthquake of magnitude 4.5 or above could cause submarine avalanches and create dangerous tsunamis with waves higher than 26 feet.

The most likely source for an East Coast tsunami would be an underwater avalanche along the continental slope.

Although the risk is small, tsunamis are possible on the East Coast of the United States from a variety of sources, according to new research.

And as Hurricane Sandy showed, the region is completely unprepared for a major influx of water, said U.S. Geological Survey researcher Uri ten Brink.

The most likely source for an East Coast tsunami would be an underwater avalanche along the continental slope, according to research presented by ten Brink and others earlier this month at the annual meeting of the Geological Society of America in Charlotte, N.C. Ten Brink also outlined several other possible sources of tsunamis, including earthquakes and even collapsing volcanoes.

Underwater avalanches

An offshore earthquake of magnitude 4.5 or above could cause submarine avalanches and create dangerous tsunamis with waves higher than 26 feet (8 meters), ten Brink told OurAmazingPlanet. Underwater canyons and bays could focus these waves and make them even bigger.

A 7.2-magnitude earthquake off the southern coast of Newfoundland in 1929 caused a large underwater landslide, creating a large wave that rushed ashore and killed 28 people on the island, ten Brink said. The waves were up to 26 feet high until some reached narrow inlets, where they grew to 43 feet (13 m), he said.

While the tsunami was catastrophic for Newfoundland, it created only small waves for most of the U.S. coast and didn’t cause any fatalities there. That’s typical of tsunamis from submarine landslides: They tend to be large for nearby areas but quickly taper off, ten Brink said.

While this is the only example of a tsunami near the East Coast in recorded history, there are plenty of areas along the continental slope – where the North American continent ends and drops into the Atlantic Ocean basin – at risk for these landslides, ten Brink said.

Ten Brink and his colleagues are currently taking core samples of sediment from the submarine canyons along the continental slope, to find evidence of past landslides and how often landslides occur, he said. His team has been working for more than five years to map these submarine canyons with sonar to highlight areas most at risk of landslides, he added.

The Puerto Rico trench

The movement of tectonic plates beneath the ocean can create waves that travel much farther than those caused by submarine landslides, because they involve the movement of a much larger volume of water, with longer waves that don’t quickly dissipate, ten Brink said. The most dangerous earthquakes are those at subduction zones, where one plate dives beneath another.

While the most infamous subduction zones are found around the Pacific Ring of Fire – such as the one that set off the massive 2011 Japan tsunami – there is indeed a subduction zone capable of creating tsunamis near the East Coast. In the northeast Caribbean, the area called the Puerto Rico trench features a subduction zone.

When the 2004 Indian Ocean tsunami hit, ten Brinks’ group received funding from the U.S. government to study the tsunami potential of the Puerto Rico trench. Although its work is still ongoing, his group has found that much of the fault doesn’t appear capable of creating an earthquake and tsunami large enough to cause big problems for the East Coast. But a tsunami originating there could cause significant destruction in the Caribbean.

University of Puerto Rico researcher Zamara Fuentes, who isn’t involved in ten Brinks’ research, said one quake in this region in 1918 created a tsunami that killed 116 people on Puerto Rico. Fuentes studies sediment cores around the Caribbean to look for evidence of past tsunamis. Based on historical records, the USGS says 27 tsunamis in the Caribbean have caused fatalities and extensive damage since the 16th century.

Risks across the Atlantic

Another possible source for East Coast tsunamis is the Azores-Gibraltar Transform Fault, off the coast of Portugal. One massive earthquake along this fault in 1755 destroyed most of Lisbon and created a tsunami recorded as far away as Brazil. It was barely noticed on the East Coast, however, ten Brink said. His group has created computer models that suggest underwater mountains west of Portugal helped reduce the impact of this tsunami by slowing the waves and disrupting their movement – and they could do the same thing in the future.

The nearby Canary Islands, off the coast of Morocco, also present a possible hazard. One large volcano on the island of La Palma, called Cumbre Vieja, could erupt, collapse and create a large tsunami capable of reaching the East Coast. A 2001 study suggested this series of events could send a 70-foot (21 m) wave crashing into the East Coast. But ten Brink said that study hasn’t held up to subsequent review, and that the wave would be unlikely to exceed several feet in height by the time it reached North America. “I don’t see it as a credible threat,” he said.

The last possible tsunami source is a slow-moving fault north of Cuba, which has caused earthquakes in the past and possibly could create a tsunami that affected Florida and the Gulf Coast. Due to the current political situation, neither Cuban nor American researchers can conduct research in the area, he said.

To get a good idea of how often tsunamis from this or any source are likely to strike the East Coast in the future, ten Brink and others are trying to peer back in time – but much remains to be discovered. “There are more questions than answers at this point,” ten Brink said.

Earth Watch Report

Geologists find East Coast quakes travel farther

By Michael Felberbaum

Associated Press

RICHMOND, Va. — Data from the 2011 earthquake centered in Virginia shows East Coast tremors can travel much farther and cause damage over larger areas than previously thought, the U.S. Geological Survey said Tuesday.

The agency estimated about one-third of the U.S. population could have felt the magnitude 5.8 tremor centered about 50 miles northwest of Richmond, which would mean more people were affected than any earthquake in U.S. history. Scientists also found the quake that caused more than $200 million in damage triggered landslides at distances four times farther and over an area 20 times larger than research from previous quakes has shown.

“Scientists are confirming with empirical data what more than 50 million people in the eastern U.S. experienced firsthand: this was one powerful earthquake,” USGS Director Marcia McNutt said in a news release about the findings presented at the Geological Society of America conference in Charlotte, N.C.

Researchers used landslides to see how far-reaching the shaking from East coast earthquakes could be. The unexpected jolt cracked the Washington Monument in spots and toppled delicate masonry high atop the National Cathedral. The shaking was felt from Georgia to New England.

According to the findings, the farthest landslide from the quake was 150 miles from the epicenter, a greater distance than any other similar-sized earthquake. Previous similar quakes have resulted in landslides no farther than 36 miles from the epicenter.

Additionally, the landslides from the 2011 tremor occurred in an area of about 12,895 square-miles — about the size of the state of Maryland. Previous studies indicated an area of about 580 square-miles — about the size of Houston — from an earthquake of similar magnitude.

“It’s just much more dangerous to have an earthquake at that level back on the East Coast than it would be on the West Coast,” said Edwin Harp, a USGS scientist and co-author of the study. “If something big happened, although it’s much less frequent, it would tend to damage a lot more buildings because they’re probably not quite up to the codes that they are in California.”

Geologic structure and rock properties on the East Coast allow seismic waves to travel farther without weakening compared with the West Coast, Harp said.

He said equations used to predict ground shaking might need to be revised now that scientists know more about the power of East Coast earthquakes.

The information also will help with building codes as well as emergency preparedness, the USGS said.

While West Coast earthquake veterans scoffed at what they viewed as only a moderate temblor, the August 2011 quake changed the way officials along the East Coast viewed emergency preparedness. Emergency response plans that once focused on hurricanes, tornadoes, flooding and snow are being revised to include quakes.

Some states have enacted laws specifically related to the quake, and there is anecdotal evidence of a spike in insurance coverage for earthquake damage.

Read more: Geologists find East Coast quakes travel farther – Washington Times http://www.washingtontimes.com/news/2012/nov/6/geologists-east-coast-earthquakes-travel-farther/print/#ixzz2BbnSN1oD
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