The , based at the 91探花, will host an online event on the 40th anniversary of the eruption of Mount St. Helens, featuring seismologists from the 91探花and other institutions who can explain the events before, during and after the historic blast.

The will take place from 6:30 to 8 p.m., Monday, May 18, on the PNSN鈥檚 YouTube channel — exactly 40 years after the blast. The group will stream prerecorded talks from four speakers and then host a live Q&A of questions on the network鈥檚 . Moderator Harold Tobin, director of the PNSN and a 91探花professor of Earth and space sciences, will select audience questions.

The presenters will review the region鈥檚 tectonics, volcanoes and volcanic hazards, and summarize how the science and monitoring has evolved over the past four decades.

, research professor emeritus of Earth and space sciences, was intimately involved with recording and interpreting the earthquake buildup to the massive eruption. His personal story of the two months leading up to the 1980 eruption will illustrate the difficulty and uncertainty of dealing with a developing natural disaster in real time.

did his doctorate at the 91探花with Malone and is now scientist-in-charge at the U.S. Geological Survey鈥檚 Cascade Volcano Observatory. He will describe the more recent activity at Mount St. Helens and the USGS work on volcano monitoring throughout the Cascades.

, a professor of geophysics at Western Washington University whose research focuses on volcanoes and landslides, will discuss plate tectonics and the origin of the Cascade volcanoes.

, professor at the University of Oregon, will discuss the individual character of different volcanoes and volcanic hazards.

For more information on the event, contact PNSN communications director Bill Steele at wsteele@uw.edu or 206-685-5880.

The study was led by scientists at the University of New Mexico with co-authors at the 91探花, Rice University and Cornell University. All are part of an ambitious effort to use remote sensing to better understand the hidden passageways beneath one of the country’s most dangerous active volcanoes.

The , published Nov. 1 in Nature Communications, analyzes compressional waves traveling through the crust and reflecting off the mantle below the volcano. Results show that on one side the mantle is largely , a rare, moisture-absorbing, dark-green mineral that can look like a snake’s skin. But the mantle below the eastern half of the mountain is mostly , a common mineral that allows water 鈥� thought to play a key role in volcanic eruptions 鈥� to percolate up and into the overlying crust.

The paper presents the latest results from a July 2014 experiment that conducted a . The National Science Foundation project, nicknamed for imaging Magma Under St Helens, set off seismic waves to see how they travel under the mountain and generate a map of the volcano’s plumbing. The new paper is part of a larger collaboration that also involves researchers from the U.S. Geological Survey, Oregon State University and the Swiss Federal Institute of Technology in Zurich.

During that experiment, researchers from the University of New Mexico placed 900 autonomous seismographs within 15 kilometers (9.3 miles) of the crater, increasing the density of instruments right around the volcano. All sensors were deployed along the road and trail system at Mount St. Helens with an average spacing of 250 meters.

The iMUSH experiment set off 23 active-source explosions, with energy similar to small 2.0 magnitude earthquakes, over a two-week period. The resulting dataset provides high-resolution seismic imaging of deep crustal structure beneath this active arc volcano.

“We show that Mount St. Helens sits atop a sharp lateral boundary in Moho reflectivity,” said corresponding author , a postdoctoral researcher at the University of New Mexico. The lack of reflections to the west can be explained if there is a relatively cold wedge of serpentinite to the west of the mountain, because the compressional wave speed of serpentine is not very different than that of the overriding crust.

In this context, cold is less than about 700 degrees C, or 1,300 degrees F. Below that temperature the serpentinite binds the water into a crystal structure. Above that temperature, however, serpentinite is not stable, and water can percolate up through the hot mantle unimpeded and into the overlying crust.

“The melt that supplies Mount St. Helens is probably formed to the east, in the mantle wedge below Mount Adams, and then moves west through the magmatic system somehow,” Hansen concluded.

91探花co-authors are and , both professors in the Department of Earth & Space Sciences. Other co-authors are Brandon Schmandt at the University of New Mexico, Alan Levander at Rice University, Eric Kiser at the University of Arizona and Geoff Abers at Cornell University.

鈥淭his is a nice result because it shows a very sharp boundary between where you have reflectivity and where you don’t, and that boundary between strong and weak reflectivity is pretty much directly beneath Mount St. Helens,鈥� Creager said. 鈥淭he density of data lets us see that this boundary between where there is reflectivity and where there isn’t is very sharp. Presumably what it’s telling us is the temperature of the mantle.”

Water is locked in various minerals inside the subducting oceanic plate. As the slab goes down, the temperature and pressure increase and the water is squeezed out of the crystals. The water then migrates up into the mantle of the overriding continental plate, where it reacts with olivine to become serpentinite to the west of Mount St. Helens, or olivine to the east. The temperature is key, Creager said, because that indicates where water in the descending ocean plate could be mixing with the rock to lower the melting temperature and form volcano-creating magma.

“An important question is: where is the water, and where isn’t it?” Creager said.

鈥淭his adds to a variety of other experiments that suggest that where it’s cold, this water is basically getting soaked into the mantle and turning olivine into serpentine and not going anywhere, so it can’t get up into the crust to form volcanoes,鈥� he said. 鈥淲hen you get up into where there is olivine, the temperature is hotter, serpentine isn’t stable, so the water can play its role in the volcanic process.鈥�

An iMUSH published in the spring that was led by Rice University suggested that most of the eruptive products came from one or more chambers at depths of 3 to 12 kilometers (about 2 to 7 miles), and that those chambers may be connected.

The full iMUSH experiment includes four different lines of analysis. The UW-led team deployed 70 three-directional seismometers to detect the tiny earthquakes that happen about twice a day, either due to movement of tectonic plates or motion of magma within the volcano, over a two-year period. 91探花researchers retrieved the instruments in August and are now analyzing their data. They hope to get a higher-resolution image of the deeper sections.

Overall, the goal is to create a more complete picture of the magma system beneath Mount St. Helens both to better understand and predict volcanic activity, and also to gauge the severity of the event when an eruption is imminent.

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For more information, contact Hansen at stevenhansen@unm.edu and Creager at 206-685-2803 or kcc@uw.edu.

Adapted from a University of New Mexico .

NSF grants: 1445937, 1520875 and 1459047

New 91探花 research shows that a common type of volcano is not just spewing molten rock from the mantle, but contains elements that suggest something more complicated is drawing material out of the descending plate of Earth’s crust.

Geologists have long believed that solidified volcanic lava, or basalt, originates in the mantle, the molten rock just below the crust. But the new study uses detailed chemical analysis to find that the basalt’s magnesium 鈥� a shiny gray element that makes up about 40 percent of the mantle but is rare in the crust 鈥� does not look like that of the mantle, and shows a surprisingly large contribution from the crust. The paper was published the week of June 13 in the .

“Although the volcanic basalt was produced from the mantle, its magnesium signature is very similar to the crustal material,” said lead author , a 91探花associate professor of Earth and space sciences. “The ocean-floor basalts are uniform in the type of magnesium they contain, and other geologists agree that on a global scale the mantle is uniform,” he said. “But now we found one type of the mantle is not.”

The study used rock samples from an inactive volcano on the Caribbean island of Martinique, a region where an ocean plate is slowly plunging, or subducting, beneath a continental plate. This situation creates an , a common type of volcano that includes those along the Pacific Ocean’s “.”

Researchers chose to study a volcano in the Caribbean partly because the Amazon River carries so much sediment from the rainforest to the seabed. One reason scientists want to pin down the makeup of volcanic material is to learn how much of the carbon-rich sediment from the surface gets carried deep in the Earth, and how much gets scraped off from the descending plate and reemerges into the planet’s atmosphere.

Analyzing the weight of magnesium atoms in the erupted basalt shows that they came not from the mantle, nor from the organic sediment scraped off during the slide, but directly from the descending oceanic crust. Yet the volcanic basalt lacks other components of the crust.

“The majority of the other ingredients are still like the mantle; the only difference is the magnesium. The question is: Why?” Teng said.

The authors hypothesize that at great depths, magnesium-rich water is squeezed from the rock that makes up Earth’s crust. As the fluid travels, the surrounding rock acts like a Brita filter that picks up the magnesium, transferring magnesium particles from the crust to the mantle just below the subduction zone.

“This is what we think is very exciting,” Teng said. “Most people think you add either crustal or mantle materials as a solid. Here we think the magnesium was added by a fluid.”

Fluids seem to play a role in seismic activity at subduction zones, Teng said, and having more clues to how those fluids travel deep in the Earth could help better understand processes such as volcanism and deep earthquakes.

He and co-author , a 91探花doctoral student in Earth and space sciences, plan to do follow-up studies on basalt rocks from the Cascade Mountains and other arc volcanoes to analyze their magnesium composition and see if this effect is widespread.

The other co-author is at the University of Grenoble in France. The research was funded by the U.S. National Science Foundation and the French National Research Agency.

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For more information, contact Teng at fteng@uw.edu or 206-543-7615.

Grants: NSF: EAR-1340160 and ANR-10-BLAN-0603

For now, such warning signs can only rely on external clues, like earthquakes and gas emissions. But a 91探花 simulation has managed to demonstrate what’s happening deep inside the volcano. The study, published Sept. 7 in , is the first to simulate the individual crystals’ movement in the magma chamber to better understand the motion of the magma and buildup of pressure.

“The thing about studying volcanoes is we can’t really see inside of them to know what’s going on,” said co-author , a 91探花doctoral student in Earth and space sciences. “Whenever there’s unrest, like earthquakes, gas emissions or surface deformation, it’s really difficult to know what processes are taking place inside the volcano.”

Each volcano has a unique personality. Volcanologists use the remains of past eruptions and previous warning signs to predict when it might blow. But those predictions are based on only vague understanding of the system’s inner workings.

The idealized 91探花computer simulation could help volcanologists better understand how energy builds up inside a system like Mauna Loa, which is a focus of the 91探花group’s research, to predict when it will erupt.

“This tool is novel because it lets us explore the mechanics,” said first author , a 91探花professor of Earth and space sciences. “It creates an interpretive framework for what controls the movement, and what might produce the signals we see on the outside.”

The team used a computer model originally developed by the U.S. Department of Energy to model fuel combustion. The 91探花group previously adapted the code to simulate volcanic eruptions and ash plumes; this paper is the first time it’s been used to go down inside the volcano and examine the movement of each individual crystal.

A volcano is filled with “magma mush,” a slushy material that is part magma, or liquid rock, and part solid crystal. Previous studies approximated it as a thick fluid. But capturing its true dual nature makes a difference, since the crystals interact in ways that matter for its motion.

“If we see earthquakes deep inside Mauna Loa, that tells us that there’s magma moving up through the volcano,” Bergantz said. “But how can we better understand its progress up through that plumbing system?”

The simulation shows the magma has three circulation states: slow, medium and fast. In the slow state, new magma just percolates up through the crystal pores. As the rate of injected magma increases, however, it creates a “mixing bowl” region where older crystals get mixed in with the new material.

“In these crystal-rich mushes, we know that we have magma going in and sometimes it might punch through [the layer of crystals at the bottom],” Schleicher said. “But we don’t know how the mixing is happening or the timescales involved.”

https://youtu.be/hT2_eLYzXmw

The current model is an idealized magma chamber, but with more computing power it could be expanded to reproduce a particular volcano’s internal structure.

Now that researchers can simulate what happens inside a magma chamber, Schleicher will look at rock samples from Mauna Loa and analyze the layers in the crystals. Crystals preserve chemical clues as they grow, similar to tree rings. Matching the model with the crystals’ composition will help recreate the rock’s history and track how magma has moved inside Mauna Loa.

“Mauna Loa is a terrific place to study because it’s very active, and the rocks contain a single type of crystal,” Bergantz said. “What we learn at Mauna Loa will allow us to make headway on other places, like Mount St. Helens, that are intrinsically more difficult.”

The research was funded by the National Science Foundation. The other co-author is at the University of Savoy Mont Blanc in France.

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For more information, contact Bergantz at 206-685-4972 or bergantz@uw.edu and Schleicher at jmschl@uw.edu. Click for more photos.

NSF grants: EAR-1049884, EAR01447266, DGE-1256082, TG-EAR140013

Thanks to a set of by the 91探花 to bring the deep sea online, what appears to be an eruption of Axial Volcano on April 23 was observed in real time by scientists on shore.

“It was an astonishing experience to see the changes taking place 300 miles away with no one anywhere nearby, and the data flowed back to land at the speed of light through the fiber-optic cable connected to Pacific City 鈥� and from there, to here on campus by the Internet, in milliseconds,” said , a 91探花professor of oceanography who led the installation of the instruments as part of a larger effort sponsored by the .

Delaney organized a on campus in mid-April at which marine scientists discussed how this high-tech observatory would support their science. Then, just before midnight on April 23 until about noon the next day, the seismic activity went off the charts.

The gradually increasing rumblings of the mountain were documented over recent weeks by , a 91探花marine geophysicist who studies such systems.

During last week’s event, the earthquakes increased from hundreds per day to thousands per day, and the center of the volcanic crater (2 meters) over the course of 12 hours.

“The only way that could have happened was to have the magma move from beneath the caldera to some other location,” Delaney said, “which the earthquakes indicate is right along the edge of the caldera on the east side.”

The seismic activity was recorded by eight that measure shaking up to 200 times per second around the caldera and at the base of the 3,000-foot seamount. The height of the caldera was tracked by the , which measures the pressure of the water overhead and then removes the effect of tides and waves to calculate its position.

The depth instrument was developed by , an oceanographer at Oregon State University and the National Oceanic and Atmospheric Administration who has also and predicted that the volcano would erupt in 2015.

The most recent eruptions were in 1998 and 2011.

The volcano is located about 300 miles west of Astoria, Oregon, on the Juan de Fuca Ridge, part of the globe-girdling mid-ocean ridge system 鈥� a continuous, 70,000 km (43,500 miles) long submarine volcanic mountain range stretching around the world like the strings on a baseball, and where about 70 percent of the planet’s volcanic activity occurs. The highly energetic Axial Seamount, Delaney said, is viewed by many scientists as being representative of the myriad processes operating continuously along the powerful subsea volcanic chain that is present in every ocean.

“This exciting sequence of events documented by the OOI-Cabled Array at Axial Seamount gives us an entirely new view of how our planet works,” said , division director for ocean sciences at the National Science Foundation. “Although the OOI-Cabled Array is not yet fully operational, even with these preliminary observations we can see how the power of innovative instrumentation has the potential to teach us new things about volcanism, earthquakes and other vitally important scientific phenomena.”

The full set of instruments in the deep-sea observatory is scheduled to come online this year. A first maintenance cruise leaves from the 91探花in early July, and will let researchers and students further explore the aftermath of the volcanic activity.

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For more information, contact Delaney at 206-543-5059 or jdelaney@uw.edu. See also a from Oregon State University. Read previous 91探花Today articles about the observatory .

They hope the research will produce science that will lead to better understanding of eruptions, which in turn could lead to greater public safety.

The project involves three distinct components: active-source seismic monitoring, passive-source seismic monitoring and magnetotelluric monitoring, using fluctuations in Earth’s electromagnetic field to produce images of structures beneath the surface.

Researchers are beginning passive-source and magnetotelluric monitoring, while active-source monitoring 鈥� measuring seismic waves generated by underground detonations 鈥� will be conducted later.

Passive-source monitoring involves burying seismometers at 70 different sites throughout a 60-by-60-mile area centered on Mount St. Helens in southwestern Washington. The seismometers will record data from a variety of seismic events.

“We will record local earthquakes, as well as distant earthquakes. Patterns in the earthquake signatures will reveal in greater detail the geological structures beneath St. Helens,” said John Vidale, director of the 91探花-based Pacific Northwest Seismic Network.

Magnetotelluric monitoring will be done at 150 sites spread over an area running 125 miles north to south and 110 miles east to west, which includes both Mount Rainier and Mount Adams. Most of the sites will only be used for a day, with instruments recording electric and magnetic field signals that will produce images of subsurface structures.

Besides the UW, collaborating institutions are Oregon State University, Lamont-Doherty Earth Observatory at Columbia University, Rice University, Columbia University, the U.S. Geological Survey and ETH-Zurich in Switzerland. The work is being funded by the National Science Foundation.

Mount St. Helens has been the most active volcano in the Cascade Range during the last 2,000 years and has erupted twice in the last 35 years. It also is more accessible than most volcanoes for people and equipment, making it a prime target for scientists trying to better understand how volcanoes get their supply of magma.

The magma that eventually comes to the surface probably originates 60 to 70 miles deep beneath St. Helens, at the interface between the Juan de Fuca and North American tectonic plates. The plates first come into contact off the Pacific Northwest coast, where the Juan de Fuca plate subducts beneath the North American plate and reaches great depth under the Cascades. As the magma works its way upward, it likely accumulates as a mass several miles beneath the surface.

As the molten rock works its way toward the surface, it is possible that it gathers in a large chamber a few miles beneath the surface. The path from great depth to this chamber is almost completely unknown and is a main subject of the study.

The project is expected to conclude in the summer of 2016.

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聽For more information, contact Vidale at 310-210-2131 or vidale@uw.edu. The lead scientist on passive-seismic monitoring is Kenneth Creager, a 91探花professor of Earth and space sciences, who can be reached at 206-685-2803 or creager@ess.washington.edu. The lead scientist for magnetotelluric monitoring is Adam Schultz, professor of geology and geophysics at Oregon State University, 541-737-9832 or adam.schultz@oregonstate.edu.

The Imaging Magma Under St. Helens website is at .

A new analysis of an eruption sequence at Alaska’s Redoubt Volcano in March 2009 shows that the harmonic tremor glided to substantially higher frequencies and then stopped abruptly just before six of the eruptions, five of them coming in succession.

“The frequency of this tremor is unusually high for a volcano, and it鈥檚 not easily explained by many of the accepted theories,” said Alicia Hotovec-Ellis, a 91探花 doctoral student in .

Documenting the activity gives clues to a volcano’s pressurization right before an explosion. That could help refine models and allow scientists to better understand what happens during eruptive cycles in volcanoes like Redoubt, she said.

The source of the earthquakes and harmonic tremor isn’t known precisely. Some volcanoes emit sound when magma 鈥� a mixture of molten rock, suspended solids and gas bubbles 鈥� resonates as it pushes up through thin cracks in the Earth’s crust.

But Hotovec-Ellis believes in this case the earthquakes and harmonic tremor happen as magma is forced through a narrow conduit under great pressure into the heart of the mountain. The thick magma sticks to the rock surface inside the conduit until the pressure is enough to move it higher, where it sticks until the pressure moves it again.

Each of these sudden movements results in a small earthquake, ranging in magnitude from about 0.5 to 1.5, she said. As the pressure builds, the quakes get smaller and happen in such rapid succession that they blend into a continuous harmonic tremor.

“Because there’s less time between each earthquake, there’s not enough time to build up enough pressure for a bigger one,” Hotovec-Ellis said. “After the frequency glides up to a ridiculously high frequency, it pauses and then it explodes.”

She is the lead author of a forthcoming in the that describes the research. Co-authors are John Vidale of the 91探花and Stephanie Prejean and Joan Gomberg of the U.S. Geological Survey.

Hotovec-Ellis is a co-author of a second paper, published online July 14 in , that introduces a new “frictional faulting” model as a tool to evaluate the tremor mechanism observed at Redoubt in 2009. The lead author of that paper is Ksenia Dmitrieva of Stanford University, and other co-authors are Prejean and Eric Dunham of Stanford.

The pause in the harmonic tremor frequency increase just before the volcanic explosion is the main focus of the Nature Geoscience paper. “We think the pause is when even the earthquakes can’t keep up anymore and the two sides of the fault slide smoothly against each other,” Hotovec-Ellis said.

She documented the rising tremor frequency, starting at about 1 hertz (or cycle per second) and gliding upward to about 30 hertz. In humans, the audible frequency range starts at about 20 hertz, but a person lying on the ground directly above the magma conduit might be able to hear the harmonic tremor when it reaches its highest point (it is not an activity she would advise, since the tremor is closely followed by an explosion).

Scientists at the USGS Alaska Volcano Observatory have dubbed the highest-frequency harmonic tremor at Redoubt Volcano “the screams” because they reach such high pitch compared with a 1-to-5 hertz starting point. Hotovec-Ellis created two recordings of the seismic activity. A covers about 10 minutes of seismic sound and harmonic tremor, sped up 60 times. A condenses about an hour of activity that includes more than 1,600 small earthquakes that preceded the first explosion with harmonic tremor.

http://soundcloud.com/uw-today/redoubtscream

http://soundcloud.com/uw-today/redoubtdrumbeats

Upward-gliding tremor immediately before a volcanic explosion also has been documented at the Arenal Volcano in Costa Rica and Soufri猫re Hills volcano on the Caribbean island of Montserrat.

“Redoubt is unique in that it is much clearer that that is what’s going on,” Hotovec-Ellis said. “I think the next step is understanding why the stresses are so high.”

The work was funded in part by the USGS and the National Science Foundation.

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聽For more information, contact Hotovec-Ellis at ahotovec@uw.edu.

But research in the last 20 years has shown that the Kamchatka Peninsula and Kuril Islands are a seismic and volcanic hotbed, with a potential to trigger tsunamis that pose a risk to the rest of the Pacific Basin.

A magnitude 9 earthquake in that region in 1952 caused significant damage elsewhere on the Pacific Rim, and even less-powerful quakes have had effects throughout the Pacific Basin.

“There’s not a large population in the Russian Far East, but it’s obviously important to the people who live there. Thousands of people were killed in tsunamis because of the earthquake in 1952. And tsunamis don’t stay home,” said Jody Bourgeois, a 91探花 professor of Earth and space sciences.

Bourgeois will discuss the seismic and volcanic threats in the Kamchatka-Kurils region Monday (Dec. 3) during the fall meeting of the in San Francisco.

Earthquakes greater than magnitude 8 struck the central Kurils in 2006 and 2007, and both produced large local tsunamis, up to about 50 feet. Though the tsunamis that crossed the Pacific were much smaller, the one from the 2006 quake did more than $10 million in damage at Crescent City, Calif.

In 2009, Sarychev Peak in the Kurils erupted spectacularly, disrupting air traffic over the North Pacific.

Clearly, determining the frequency of such events is important to many people over a broad area, Bourgeois said.

“Let’s say you decide to build a nuclear power plant in Crescent City. You have to consider local events, but you also have to consider non-local events, worst-case scenarios, which includes tsunamis coming across the Pacific,” she said.

But that is only possible by understanding the nature of the hazards, and the historic record for earthquakes, tsunamis and volcanic eruptions in Kamchatka and the Kurils is relatively short. In addition, because the region was closed off from much of the world for decades, much of the information has started becoming available only recently.

Much has been learned in the last 10 years in the examination of tsunami deposits and other evidence of prehistoric events, Bourgeois said, but more field work in the Kamchatka-Kurils subduction zone is required to get a clearer picture.

“For hazard analysis, you should just assume that a subduction zone can produce a magnitude 9 earthquake,” she said. So it is important to “pay attention to the prehistoric record” to know where, and how often, such major events occur.

Bourgeois noted that in the last 25 years research in the Cascadia subduction zone off the coast of Washington, Oregon, northern California and British Columbia has demonstrated that the historic record does not provide a good characterization of the hazard. It was once assumed the risks in the Northwest were small, but the research has shown that, before there were any written records, Cascadia produced at least one magnitude 9 earthquake and a tsunami that struck Japan.

Alaska’s Aleutian Islands and the Komandorsky Islands, an extension of the Aleutians controlled by Russia, are another source of seismic and volcanic activity that need to be evaluated for their potential risk beyond what is known from the historical record.

“The Aleutians are under-studied,” Bourgeois said. “The work in the Russian Far East is kind of a template for the Aleutians.”

Ideally, a dedicated boat could ferry researchers to a number of islands in the Aleutian chain, similar to how Bourgeois and other scientists from the United States, Japan and Russia have carried out a detailed research project in the Kuril Islands in the last decade.

聽聽聽聽聽聽聽聽聽聽聽 “The problem is that during the (research) field season, boats are commonly in demand for fishing,” she said.

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聽For more information, contact Bourgeois at 206-685-2443 or jbourgeo@uw.edu.