September 2018

Zirconia: The World’s Hottest Rock

Earth History, Geochemistry, Rocks 7:31 PM

Zirconia: The World’s Hottest Rock

zirconia Zirconia is a mineral with a crystal structure made from the elements zirconium (Zr) and oxygen (O), with the chemical formu...

Scientists Have Been Drilling Into the Ocean Floor for 50 Years – Here's What They've Found So Far

ocean, Researches 7:21 PM

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<tr><td class="tr-caption" style="text-align: center;">Ocean Floor photo: By David Shukman</td></tr>
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It's stunning but true that we know more about the surface of the moon than about the Earth's ocean floor. Much of what we do know has come from scientific ocean drilling – the systematic collection of core samples from the deep seabed. This revolutionary process began 50 years ago, when the drilling vessel Glomar Challenger sailed into the Gulf of Mexico on August 11, 1968 on the first expedition of the federally funded Deep Sea Drilling Project.<br />
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I went on my first scientific ocean drilling expedition in 1980, and since then have participated in six more expeditions to locations including the far North Atlantic and Antaractica's Weddell Sea. In my lab, my students and I work with core samples from these expeditions.<br />
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Each of these cores, which are cylinders 31 feet long and 3 inches wide, is like a book whose information is waiting to be translated into words. Holding a newly opened core, filled with rocks and sediment from the Earth's ocean floor, is like opening a rare treasure chest that records the passage of time in Earth's history.<br />
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Over a half-century, scientific ocean drilling has proved the theory of plate tectonics, created the field of paleoceanography and redefined how we view life on Earth by revealing an enormous variety and volume of life in the deep marine biosphere. And much more remains to be learned.<br />
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<span style="font-family: "georgia" , "times new roman" , serif;">Technological innovations</span></h4>
Two key innovations made it possible for research ships to take core samples from precise locations in the deep oceans. The first, known as dynamic positioning, enables a 471-foot ship to stay fixed in place while drilling and recovering cores, one on top of the next, often in over 12,000 feet of water.<br />
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Anchoring isn't feasible at these depths. Instead, technicians drop a torpedo-shaped instrument called a transponder over the side. A device called a transducer, mounted on the ship's hull, sends an acoustic signal to the transponder, which replies. Computers on board calculate the distance and angle of this communication. Thrusters on the ship's hull maneuver the vessel to stay in exactly the same location, countering the forces of currents, wind and waves.<br />
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Another challenge arises when drill bits have to be replaced mid-operation. The ocean's crust is composed of igneous rock that wears bits down long before the desired depth is reached.<br />
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When this happens, the drill crew brings the entire drill pipe to the surface, mounts a new drill bit and returns to the same hole. This requires guiding the pipe into a funnel shaped re-entry cone, less than 15 feet wide, placed in the bottom of the ocean at the mouth of the drilling hole. The process, which was first accomplished in 1970, is like lowering a long strand of spaghetti into a quarter-inch-wide funnel at the deep end of an Olympic swimming pool.<br />
<h4 style="text-align: left;">
<span style="font-family: "georgia" , "times new roman" , serif;">Confirming plate tectonics</span></h4>
When scientific ocean drilling began in 1968, the theory of plate tectonics was a subject of active debate. One key idea was that new ocean crust was created at ridges in the seafloor, where oceanic plates moved away from each other and magma from earth's interior welled up between them. According to this theory, crust should be new material at the crest of ocean ridges, and its age should increase with distance from the crest.<br />
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The only way to prove this was by analyzing sediment and rock cores. In the winter of 1968-1969, the Glomar Challenger drilled seven sites in the South Atlantic Ocean to the east and west of the Mid-Atlantic ridge. Both the igneous rocks of the ocean floor and overlying sediments aged in perfect agreement with the predictions, confirming that ocean crust was forming at the ridges and plate tectonics was correct.<br />
<h4 style="text-align: left;">
<span style="font-family: "georgia" , "times new roman" , serif;">Reconstructing earth's history</span></h4>
The ocean record of Earth's history is more continuous than geologic formations on land, where erosion and redeposition by wind, water and ice can disrupt the record. In most ocean locations sediment is laid down particle by particle, microfossil by microfossil, and remains in place, eventually succumbing to pressure and turning into rock.<br />
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Microfossils (plankton) preserved in sediment are beautiful and informative, even though some are smaller than the width of a human hair. Like larger plant and animal fossils, scientists can use these delicate structures of calcium and silicon to reconstruct past environments.<br />
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Thanks to scientific ocean drilling, we know that after an asteroid strike killed all non-avian dinosaurs 66 million years ago, new life colonized the crater rim within years, and within 30,000 years a full ecosystem was thriving. A few deep ocean organisms lived right through the meteorite impact.<br />
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Ocean drilling has also shown that ten million years later, a massive discharge of carbon – probably from extensive volcanic activity and methane released from melting methane hydrates – caused an abrupt, intense warming event, or hyperthermal, called the Paleocene-Eocene Thermal Maximum. During this episode, even the Arctic reached over 73 degrees Fahrenheit.<br />
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The resulting acidification of the ocean from the release of carbon into the atmosphere and ocean caused massive dissolution and change in the deep ocean ecosystem.<br />
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This episode is an impressive example of the impact of rapid climate warming. The total amount of carbon released during the PETM is estimated to be about equal to the amount that humans will release if we burn all of Earth's fossil fuel reserves. Yet, an important difference is that the carbon released by the volcanoes and hydrates was at a much slower rate than we are currently releasing fossil fuel. Thus we can expect even more dramatic climate and ecosystem changes unless we stop emitting carbon.<br />
<h4 style="text-align: left;">
<span style="font-family: "georgia" , "times new roman" , serif;">Finding life in ocean sediments</span></h4>
Scientific ocean drilling has also shown that there are roughly as many cells in marine sediment as in the ocean or in soil. Expeditions have found life in sediments at depths over 8000 feet; in seabed deposits that are 86 million years old; and at temperatures above 140 degrees Fahrenheit.<br />
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Today scientists from 23 nations are proposing and conducting research through the International Ocean Discovery Program, which uses scientific ocean drilling to recover data from seafloor sediments and rocks and to monitor environments under the ocean floor. Coring is producing new information about plate tectonics, such as the complexities of ocean crust formation, and the diversity of life in the deep oceans.<br />
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This research is expensive, and technologically and intellectually intense. But only by exploring the deep sea can we recover the treasures it holds and better understand its beauty and complexity.<br />
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<br />
<u><i><span style="font-family: "trebuchet ms" , sans-serif;">The above post is reprinted from <a href="https://theconversation.com/scientists-have-been-drilling-into-the-ocean-floor-for-50-years-heres-what-theyve-found-so-far-100309" rel="nofollow" target="_blank">The Conversation</a> under a Creative Commons license.</span></i></u></div>

Scientists Have Been Drilling Into the Ocean Floor for 50 Years – Here's What They've Found So Far

Ocean Floor photo: By David Shukman It's stunning but true that we know more about the surface of the moon than about the Earth...

Japan's Largest Complete Dinosaur Skeleton Comes to Life

dinosaur, Earth History 7:40 PM

Japan's Largest Complete Dinosaur Skeleton Comes to Life

The bones of the dinosaur Mukawaryu which have been cleaned so far. These likely represent more than half of the bones the dinosaur had. ...

World's Oldest Known Animal Identified After Decades-long Mystery

Earth History, Fossils 7:03 PM

World's Oldest Known Animal Identified After Decades-long Mystery

This is a Dickinsonia fossil. The oldest known animal in the geological record has been identified, in a discovery that scientists ar...

Subducting Slabs of the Earth's Crust May Generate Unusual Features Spotted Near the Core

earth, Tectonic 7:13 PM

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Nearly 1,800 miles below the earth's surface, there are large odd structures lurking at the base of the mantle, sitting just above the core. The mantle is a thick layer of hot, mostly plastic rock that surrounds the core; atop the mantle is the thin shell of the earth's crust. On geologic time scales, the mantle behaves like a viscous liquid, with solid elements sinking and rising through its depths.<br />
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The aforementioned odd structures, known as ultra-low velocity zones (ULVZs), were first discovered in 1995 by Caltech's Don Helmberger. ULVZs can be studied by measuring how they alter the seismic waves that pass through them. But observing is not necessarily understanding. Indeed, no one is really sure what these structures are.<br />
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ULVZs are so-named because they significantly slow down the speeds of seismic waves; for example, they slow down shear waves (oscillating seismic waves capable of moving through solid bodies) by as much as 30 percent. ULVZs are several miles thick and can be hundreds of miles across. Several are scattered near the earth's core roughly beneath the Pacific Rim. Others are clustered underneath North America, Europe, and Africa.<br />
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"ULVZs exist so deep in the inner earth that they are impossible to study directly, which poses a significant challenge when trying to determine what exactly they are," says Helmberger, Smits Family Professor of Geophysics, Emeritus.<br />
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Earth scientists at Caltech now say they know not just what ULVZs are made of, but where they come from. Using experimental methods at high pressures, the researchers, led by Professor of Mineral Physics Jennifer Jackson, have found that ULVZs consist of chunks of a magnesium/iron oxide mineral called magnesiowüstite that could have precipitated out of a magma ocean that is thought to have existed at the base of the mantle millions of years ago.<br />
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The other leading theory for ULVZs formation had suggested that they consist of melted material, some of it possibly leaking up from the core.<br />
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Jackson and her colleagues, who reported on their work in a recent paper in the Journal of Geophysical Research: Solid Earth, found evidence supporting the magnesiowüstite theory by studying the mineral's elastic (or seismic) anisotropy; elastic anisotropy is a variation in the speed at which seismic waves pass through a mineral depending on their direction of travel.<br />
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One particularly unusual characteristic of the region where ULVZs exist—the core-mantle boundary (CMB)—is that it is highly heterogenous (nonuniform in character) as well as anisotropic. As a result, the speed at which seismic waves travel through the CMB varies based not only on the region that the waves are passing through but on the direction in which those waves are moving. The propagation direction, in fact, can alter the speed of the waves by a factor of three.<br />
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"Previously, scientists explained the anisotropy as the result of seismic waves passing through a dense silicate material. What we're suggesting is that in some regions, it is largely due to the alignment of magnesiowüstite within ULVZs," says Jackson.<br />
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At the pressures and temperatures experienced at the earth's surface, magnesiowüstite exhibits little anisotropy. However, Jackson and her team found that the mineral becomes strongly anisotropic when subjected to pressures comparable to those found in the lower mantle.<br />
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Jackson and her colleagues discovered this by placing a single crystal of magnesiowüstite in a diamond anvil cell, which is essentially a tiny chamber located between two diamonds. When the rigid diamonds are compressed against one another, the pressure inside the chamber rises.<br />
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Jackson and her colleagues then bombarded the sample with x-rays. The interaction of the x-rays with the sample acts as a proxy for how seismic waves will travel through the material. At a pressure of 40 gigapascals—equivalent to the pressure at the lower mantle—magnesiowüstite was significantly more anisotropic than seismic observations of ULVZs.<br />
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In order to create objects as large and strongly anisotropic as ULVZs, only a small amount of magnesiowüstite crystals need to be aligned in one specific direction, probably due to the application of pressure from a strong outside force. This could be explained by a subducting slab of the earth's crust pushing its way to the CMB, Jackson says. (Subduction occurs at certain boundaries between earth's tectonic plates, where one plate dives below another, triggering volcanism and earthquakes.)<br />
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"Scientists are still in the process of discovering what happens to the crust when it's subducted into the mantle," Jackson says. "One possibility, which our research now seems to support, is that these slabs push all the way down to the core-mantle boundary and help to shape ULVZs."<br />
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Next, Jackson plans to explore the interaction of subducting slabs, ULVZs, and their seismic signatures. Interpreting these features will help place constraints on processes that happened early in Earth's history, she says.<br />
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The study is titled "Strongly Anisotropic Magnesiowüstite in Earth's Lower Mantle."<br />
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<u><i><span style="font-family: "trebuchet ms" , sans-serif;">The study was published in the <a href="http://dx.doi.org/10.1029/2017JB015349" rel="nofollow" target="_blank">Journal of Geophysical Research.</a></span></i></u></div>

Subducting Slabs of the Earth's Crust May Generate Unusual Features Spotted Near the Core

Nearly 1,800 miles below the earth's surface, there are large odd structures lurking at the base of the mantle, sitting just above ...

Scientists Identified Three Reasons Responsible for Earth’s Spin Axis Drift

earth, Earth's magnetic field 6:29 PM

Scientists Identified Three Reasons Responsible for Earth’s Spin Axis Drift

The observed direction of polar motion, shown as a light blue line, compared with the sum (pink line) of the influence of Greenland ice l...

Thawing Permafrost May Release More CO2 Than Previously Thought

climate, Environment 5:51 PM

Thawing Permafrost May Release More CO2 Than Previously Thought

Pictured here is a permafrost thaw slump that is exposing sediment- and ice-rich permafrost on the Peel Plateau in Canada's Northwest...

Geoscientists Find Unexpected 'Deep Creep' Near San Andreas, San Jacinto Faults

Earthquakes, San Andreas, Tectonic 5:55 PM

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<tr><td class="tr-caption" style="text-align: center;">A cartoon showing how anomalous earthquakes near the San Andreas and San Jacinto faults in southern California work in regions deep below the Earth's surface. A UMass Amherst analysis shows this enigmatic pattern in the San Bernardino basin is not typical, and the authors encourage geoscientists to account for them in assessing future fault loading. Credit: UMass Amherst/Michele Cooke</td></tr>
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<span style="font-family: "georgia" , "times new roman" , serif;">Thousands of tiny earthquakes have helped expose unusual rumblings taking place beneath the surface of southern California.</span><br />
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A new analysis of thousands of very small earthquakes that have occurred in the San Bernardino basin near the San Andreas and San Jacinto faults suggests that the unusual deformation of some—they move in a different way than expected—may be due to "deep creep" 10 km below the Earth's surface, say geoscientists at the University of Massachusetts Amherst.<br />
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The new understanding should support more refined assessments of fault loading and earthquake rupture risk in the region, they add. Writing in the current online Geophysical Research Letters, doctoral student Jennifer Beyer and her advisor, geosciences professor Michele Cooke say the enigmatic behavior is seen in about one third of the hundreds of tiny quakes recorded during the lull between big damaging quakes, and their possible significance had not been appreciated until now.<br />
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Cooke says, "These little earthquakes are a really rich data set to work with, and going forward if we pay more attention than we have in the past to the details they are telling us, we can learn more about active fault behavior that will help us better understand the loading that leads up to large damaging earthquakes."<br />
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Over the past 36 years, the authors point out, seismic stations have recorded the style of deformation for thousands of small earthquakes in California's San Bernardino basin. They state, "Findings of this study demonstrate that small earthquakes that occur adjacent to and between faults can have very different style of deformation than the large ground rupturing earthquakes produced along active faults. This means that scientists should not use the information recorded by these small earthquakes in the San Bernardino basin to predict loading of the nearby San Andreas and San Jacinto faults."<br />
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Cooke explains that the usual type of fault in the region is called a strike-slip fault, where the motion is one of blocks sliding past each other. The less common kind, with "anomalous slip-sense," is an extending fault, where the motion between blocks is like a wave pulling away from the beach, one block dropping at an angle away from the other, "extending" the fault. "These only occur in this one small area, and nobody knew why," she points out. "We did the modeling that helps to explain the enigmatic data."<br />
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This is an area where Cooke, an expert in 3-D fault modeling, has done research of her own and where she is familiar with the broader research field, so she decided to try to model what is happening. She began with a hypothesis based on her earlier 3-D modeling in the area that had replicated long-term deformation over thousands of years.<br />
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"I noticed that this basin was in extension in those models unlike the surrounding regions of strike-slip," she says. "The extension was limited to within the basin just like the pattern of the anomalous extensional earthquakes. That gave me a clue that maybe those faults weren't locked as they should be between big earthquakes, but that at depths below 10 km, they were creeping."<br />
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"The typical way we look for creep is to use GPS stations set up on each side of the fault. Over time, you can note that there is movement; the faults are creeping slowly apart. The problem here is that the San Andreas and the San Jacinto faults are so close together that the GPS is unable to resolve if there is creep or not. That's why no one had seen this before. The traditional way to detect it was not able to do so."<br />
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Cooke adds, "In this paper we've shown that there is a way to have these weird tiny earthquakes all the time next to the San Jacinto Fault below 10 km, which is where deep creep may be happening. We show that it's plausible and can account for nearby enigmatic earthquakes. The model may not be perfectly correct, but it's consistent with observations."<br />
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As noted, this work has implications for assessing fault loading, Beyer and Cooke point out. Until now, seismologists have assumed that faults in the region are locked—no creep is taking place—and they use data from all the little earthquakes to infer loading on the primary faults. However, Cooke and Beyer write, "scientists should not use the information recorded by these small earthquakes in the San Bernardino basin to predict loading of the nearby San Andreas and San Jacinto faults."<br />
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Cooke adds, "Our earthquake catalog is growing every year; we can see smaller and smaller ones every year, so we thought why not take advantage of the networks we've built and we can look at them in more detail.<br />
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We don't want to wait around for the faults to move in a damaging earthquake, we want to take advantage of all the tinier earthquakes happening all the time in order to understand how the San Andreas and San Jacinto are loaded. If we can understand how they are being loaded maybe we can understand better when these faults will going to rupture."<br />
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<u><i><span style="font-family: "trebuchet ms" , sans-serif;">The study was published in the journal <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL078932" rel="nofollow" target="_blank">Geophysical Research Letters</a>.</span></i></u></div>

Geoscientists Find Unexpected 'Deep Creep' Near San Andreas, San Jacinto Faults

A cartoon showing how anomalous earthquakes near the San Andreas and San Jacinto faults in southern California work in regions deep below...

Lava Flow Seen on Restless Alaska Volcano

USA, volcano 8:34 PM

Lava Flow Seen on Restless Alaska Volcano

Veniaminof volcano Mount Veniaminof, 772 kilometres southwest of Anchorage, is one of the state's most active volcanoes A...

Study: Kidney Stones Have Distinct Geological Histories

Researches 6:08 PM

Study: Kidney Stones Have Distinct Geological Histories

A human kidney stones from Mayo Clinic. A geologist, a microscopist and a doctor walk into a lab and, with their colleagues from acro...

Geologists Reveal Ancient Connection Between England and France

Earth History, Tectonic 6:59 PM

Geologists Reveal Ancient Connection Between England and France

This graphic shows how the ancient land masses of Laurentia, Avalonia and Armorica would have collided to create the countries of England...

Elephant Bird Mystery Solved? Discovery May Explain Demise of World's Largest-ever Birds

Earth History, extinction, Fossils 6:45 PM

Elephant Bird Mystery Solved? Discovery May Explain Demise of World's Largest-ever Birds

Aepyornis maximus. Analysis of bones, from what was once the world's largest bird, has revealed that humans arrived on the tropica...

Michigan Man Discovers Glowing, Fluorescent Rocks Called "Yooperlites"

Mining, News, Rocks, USA 7:49 PM

Michigan Man Discovers Glowing, Fluorescent Rocks Called "Yooperlites"

A Michigan man who discovered a new rock type uses a black light to search for the distinctive glowing rocks along the beaches of Lake Su...

Gold 'Mother Lode' Unearthed Underground in Australia Delivers $15 Million in Just Four Days

Gold, Mining 8:13 PM

Gold 'Mother Lode' Unearthed Underground in Australia Delivers $15 Million in Just Four Days

These gold-covered rocks weigh in at 90kg and 60kg respectively. Workers at the Beta Hunt mine near the small town of Kambalda, 630 k...

Scientists Discover a Volcanic Heat Source Beneath Antarctic's Most Vulnerable Glacier

Antarctic, earth, volcano 7:58 PM

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<span style="font-family: "georgia" , "times new roman" , serif;">Active volcano discovered beneath Antarctic ice sheet could be contributing to rapidly melting glacier</span><br />
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A researcher from the University of Rhode Island's Graduate School of Oceanography and five other scientists have discovered an active volcanic heat source beneath the Pine Island Glacier in Antarctica.<br />
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The discovery and other findings, which are critical to understanding the stability of the West Antarctic Ice Sheet, of which the Pine Island Glacier is a part, are published in the paper, "Evidence of an active volcanic heat source beneath the Pine Island Glacier," in the latest edition of Nature Communications.<br />
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Assistant Professor Brice Loose of Newport, a chemical oceanographer at GSO and the lead author, said the paper is based on research conducted during a major expedition in 2014 to Antarctica led by scientists from the United Kingdom. They worked aboard an icebreaker, the RRS James Clark Ross, from January to March, Antarctica's summer.<br />
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"We were looking to better understand the role of the ocean in melting the ice shelf," Loose said. "I was sampling the water for five different noble gases, including helium and xenon. I use these noble gases to trace ice melt as well as heat transport. Helium-3, the gas that indicates volcanism, is one of the suite of gases that we obtain from this tracing method.<br />
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"We weren't looking for volcanism, we were using these gases to trace other actions," he said. "When we first started seeing high concentrations of helium-3, we thought we had a cluster of bad or suspicious data."<br />
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The West Antarctic Ice Sheet lies atop a major volcanic rift system, but there had been no evidence of current magmatic activity, the URI scientist said. The last such activity was 2,200 years ago, Loose said. And while volcanic heat can be traced to dormant volcanoes, what the scientists found at Pine Island was new.<br />
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In the paper, Loose said that the volcanic rift system makes it difficult to measure heat flow to the West Antarctic Ice Sheet. "You can't directly measure normal indicators of volcanism—heat and smoke— because the volcanic rift is below many kilometers of ice," Loose said<br />
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But as the team conducted its research, it found high quantities of an isotope of helium, which comes almost exclusively from mantle, Loose said. "When you find helium-3, it's like a fingerprint for volcanism. We found that it is relatively abundant in the seawater at the Pine Island shelf.<br />
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He said the amount of ice sliding into the ocean is measured in gigatons. A gigaton equals 1 billion metric tons.<br />
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However, Loose cautions, this does not imply that volcanism is the major source of mass loss from Pine Island. On the contrary, "there are several decades of research documenting the heat from ocean currents is destabilizing Pine Island Glacier, which in turn appears to be related to a change in the climatological winds around Antarctica," Loose said. Instead, this evidence of volcanism is a new factor to consider when monitoring the stability of the ice sheet.<br />
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The scientists report in the paper that "helium isotope and noble gas measurements provide geochemical evidence of sub-glacial meltwater production that is subsequently transported to the cavity of the Pine Island Ice Shelf." They say that heat energy released by the volcanoes and hydrothermal vents suggests that the heat source beneath Pine Island is about 25 times greater than the bulk of heat flux from an individual dormant volcano.<br />
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Professor Karen Heywood, from the University of East Anglia in Norwich, the United Kingdom, and chief scientist for the expedition, said: "The discovery of volcanoes beneath the Antarctic ice sheet means that there is an additional source of heat to melt the ice, lubricate its passage toward the sea, and add to the melting from warm ocean waters. It will be important to include this in our efforts to estimate whether the Antarctic ice sheet might become unstable and further increase sea level rise."<br />
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Does that mean that global climate change is not a factor in the stability of the Pine Island Glacier?<br />
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No, said Loose. "Climate change is causing the bulk of glacial melt that we observe, and this newly discovered source of heat is having an as-yet undetermined effect, because we do not know how this heat is distributed beneath the ice sheet."<br />
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He said other studies have shown that melting caused by climate change is reducing the size and weight of the glacier, which reduces the pressure on the mantle, allowing greater heat from the volcanic source to escape and then warm the ocean water.<br />
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"Predicting the rate of sea level rise is going to be a key role for science over the next 100 years, and we are doing that. We are monitoring and modeling these glaciers," Loose said.<br />
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The scientists conclude by writing: "The magnitude and the variations in the rate of the volcanic heat supplied to the Pine Island Glacier, either by internal magma migration, or by an increase in volcanism as a consequence of ice sheet thinning, may impact the future dynamics of the Pine Island Glacier, during the contemporary period of climate-driven glacial retreat."<br />
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<i><u><span style="font-family: "verdana" , sans-serif;">The study was published in <a href="https://www.nature.com/articles/s41467-018-04421-3" rel="nofollow" target="_blank">the journal Nature Communications.</a></span></u></i></div>

Scientists Discover a Volcanic Heat Source Beneath Antarctic's Most Vulnerable Glacier

Active volcano discovered beneath Antarctic ice sheet could be contributing to rapidly melting glacier A researcher from the Univers...

M5.9 Earthquake Detected Off Oregon Coast

7:11 PM

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A strong earthquake has hit the off coast region of Oregon on Thursday morning, according to United States Geological Survey earthquake alerts.<br />
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A 5.9-magnitude earthquake was detected Thursday morning off the Oregon Coast.<br />
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At 8:02 a.m., the National Geological Survey placed the earthquake's epicenter about 192 miles west of Coos Bay on Oregon's south coast.<br />
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No tsunami is expected on the coastline, according to the National Tsunami Warning Center.<br />
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The earthquake was preceded by a 3.7-magnitude earthquake about 32 miles closer to the Oregon coastline detected at 7:25 a.m.<br />
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Both of today's earthquakes follow a 6.3-magnitude earthquake a week ago in the same region.</div>
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Prelim M5.9 Earthquake off the coast of Oregon Sep-05 15:02 UTC, updates <a href="https://t.co/aEyIKnuGd3">https://t.co/aEyIKnuGd3</a></div>
— USGS Big Quakes (@USGSBigQuakes) <a href="https://twitter.com/USGSBigQuakes/status/1169631790748839936?ref_src=twsrc%5Etfw">September 5, 2019</a></blockquote>
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