This image shows the huge plume of sulphur dioxide that spewed from Chile’s Puyehue-Cordón Caulle Volcanic Complex, which lies in the Andes about 600 km south of Santiago. It was generated on June 6 using data from the Infrared Atmospheric Sounding Interferometer on the MetOp-A satellite and represents sulfur dioxide concentrations within the full vertical column of atmosphere. As the eruption continued, the image shows how strong winds initially swept the broad plume of sulfur dioxide northwards and then eastwards across Argentina and out over the southern Atlantic Ocean. The MetOp program was jointly established by ESA and Eumetsat and forms the space segment of Eumetsat’s Polar System. – Université Libre de Bruxelles (ULB)
This image shows the huge plume of sulphur dioxide that spewed from Chile’s Puyehue-Cordón Caulle Volcanic Complex, which lies in the Andes about 600 km south of Santiago.
After lying dormant for more than 50 years, a series of rumbling earthquakes signalled the beginnings of this major volcanic eruption. On 4 June, a fissure opened, sending a towering plume of volcanic ash and gas over 10 km high. Several thousand people were evacuated as a thick layer of ash and pumice fell and blanketed a wide area. Airports in Chile and Argentina were closed as a result.
The image was generated on 6 June using data from the Infrared Atmospheric Sounding Interferometer on Eumetsat’s MetOp-A satellite. As the eruption continued, the image shows how strong winds initially swept the broad plume of sulphur dioxide northwards and then eastwards across Argentina and out over the southern Atlantic Ocean.
Strong westerly winds are common in this region because it lies within the belt of the ‘Roaring Forties’. Since there is little land south of 40º, higher wind speeds can develop than at the same latitudes in the Northern Hemisphere.
Interestingly, over the South Atlantic, the plume take a sharp turn to the north as a pressure system causes the wind to change direction.
The Puyehue-Cordón Caulle complex is a chain of volcanoes that includes the Puyehue volcano, the Cordilera Nevada caldera and the Cordón Caulle rift zone. This event appears to have stemmed from the rift zone and is the most serious since the eruption of 1960, also from the same vent.
Chile has more than 3000 volcanoes, of which around 80 are currently active.
The image represents sulphur dioxide concentrations within the full vertical column of atmosphere. It was generated using data from the interferometer, which was developed by the French space agency CNES for MetOp-A.
Note: This story has been adapted from a news release issued by the European Space Agency
Compaction bands at multiple scales ranging from the field scale to the specimen scale to the meso and grain scale. At the field scale, picture shows the presence of narrow tabular structures within the host rock in the Valley of Fire. At the grain scale, images show clear differences in porosity (dark spots) density. This research aims at quantifying the impact of grain scale features in macroscopic physical properties that control behavior all the way to the field scale. – José Andrade/Caltech
When geologists survey an area of land for the potential that gas or petroleum deposits could exist there, they must take into account the composition of rocks that lie below the surface. Take, for instance, sandstone-a sedimentary rock composed mostly of weakly cemented quartz grains. Previous research had suggested that compaction bands-highly compressed, narrow, flat layers within the sandstone-are much less permeable than the host rock and might act as barriers to the flow of oil or gas.
Now, researchers led by José Andrade, associate professor of civil and mechanical engineering at the California Institute of Technology (Caltech), have analyzed X-ray images of Aztec sandstone and revealed that compaction bands are actually more permeable than earlier models indicated. While they do appear to be less permeable than the surrounding host rock, they do not appear to block the flow of fluids. Their findings were reported in the May 17 issue of Geophysical Research Letters.
The study includes the first observations and calculations that show fluids have the ability to flow in sandstone that has compaction bands. Prior to this study, there had been inferences of how permeable these formations were, but those inferences were made from 2D images. This paper provides the first permeability calculations based on actual rock samples taken directly from the field in the Valley of Fire, Nevada. From the data they collected, the researchers concluded that these formations are not as impermeable as previously believed, and that therefore their ability to trap fluids-like oil, gas, and CO2-should be measured based on 3D images taken from the field.
“These results are very important for the development of new technologies such as CO2 sequestration-removing CO2 from the atmosphere and depositing it in an underground reservoir-and hydraulic fracturing of rocks for natural gas extraction,” says Andrade. “The quantitative connection between the microstructure of the rock and the rock’s macroscopic properties, such as hydraulic conductivity, is crucial, as physical processes are controlled by pore-scale features in porous materials. This work is at the forefront of making this quantitative connection.”
The research team connected the rocks’ 3D micromechanical features-such as grain size distribution, which was obtained using microcomputed tomography images of the rocks to build a 3D model-with quantitative macroscopic flow properties in rocks from the field, which they measured on many different scales. Those measurements were the first ever to look at the three-dimensional ability of compaction bands to transmit fluid. The researchers say the combination of these advanced imaging technologies and multiscale computational models will lead to unprecedentedly accurate measurements of crucial physical properties, such as permeability, in rocks and similar materials.
Andrade says the team wants to expand these findings and techniques. “An immediate idea involves the coupling of solid deformation and chemistry,” he says. “Accounting for the effect of pressures and their potential to exacerbate chemical reactions between fluids and the solid matrix in porous materials, such as compaction bands, remains a fundamental problem with multiple applications ranging from hydraulic fracturing for geothermal energy and natural gas extraction, to applications in biological tissue for modeling important processes such as osteoporosis. For instance, chemical reactions take place as part of the process utilized in fracturing rocks to enhance the extraction of natural gas.”
Note: This story has been adapted from a news release issued by the California Institute of Technology
Crystals of highly carbon-13-depleted carbonate are observed using a light microscope. – Thomas Bristow
There’s a theory about how the Marinoan ice age-also known as the “Snowball Earth” ice age because of its extreme low temperatures-came to an abrupt end some 600 million years ago. It has to do with large amounts of methane, a strong greenhouse gas, bubbling up through ocean sediments and from beneath the permafrost and heating the atmosphere.
The main physical evidence behind this theory has been samples of cap dolostone from south China, which were known to have a lot less of the carbon-13 isotope than is normally found in these types of carbonate rocks. (Dolostone is a type of sedimentary rock composed of the carbonate mineral, dolomite; it’s called cap dolostone when it overlies a glacial deposit.) The idea was that these rocks formed when Earth-warming methane bubbled up from below and was oxidized-“eaten”-by microbes, with its carbon wastes being incorporated into the dolostone, thereby leaving a signal of what had happened to end the ice age. The idea made sense, because methane also tends to be low in carbon-13; if carbon-13-depeleted methane had been made into rock, that rock would indeed also be low in carbon-13. But the idea was controversial, too, since there had been no previous isotopic evidence in carbonate rock of methane-munching microbes that early in Earth’s history.
And, as a team of scientists led by researchers from the California Institute of Technology (Caltech) report in this week’s issue of the journal Nature, it was also wrong-at least as far as the geologic evidence they looked at goes. Their testing shows that the rocks on which much of that ice-age-ending theory was based were formed millions of years after the ice age ended, and were formed at temperatures so high there could have been no living creatures associated with them.
“Our findings show that what happened in these rocks happened at very high temperatures, and abiologically,” says John Eiler, the Robert P. Sharp Professor of Geology and professor of geochemistry at Caltech, and one of the paper’s authors. “There is no evidence here that microbes ate methane as food. The story you see in this rock is not a story about ice ages.”
To tell the rocks’ story, the team used a technique Eiler developed at Caltech that looks at the way in which rare isotopes (like the carbon-13 in the dolostone) group, or “clump,” together in crystalline structures like bone or rock. This clumping, it turns out, is highly dependent upon the temperature of the immediate environment in which the crystals form. Hot temperatures mean less clumping; low temperatures mean more.
“The rocks that we analyzed for this study have been worked on before,” says Thomas Bristow, the paper’s first author and a former postdoc at Caltech who is now at NASA Ames Research Center, “but the unique advance available and developed at Caltech is the technique of using carbonate clumped-isotopic thermometry to study the temperature of crystallization of the samples. It was primarily this technique that brought new insights regarding the geological history of the rocks.”
What the team’s thermometer made very clear, says Eiler, is that “the carbon source was not oxidized and turned into carbonate at Earth’s surface. This was happening in a very hot hydrothermal environment, underground.”
In addition, he says, “We know it happened at least millions of years after the ice age ended, and probably tens of millions. Which means that whatever the source of carbon was, it wasn’t related to the end of the ice age.”
Since this rock had been the only carbon-isotopic evidence of a Precambrian methane seep, these findings bring up a number of questions-questions not just about how the Marinoan ice age ended, but about Earth’s budget of methane and the biogeochemistry of the ocean.
“The next stage of the research is to delve deeper into the question of why carbon-13-depleted carbonate rocks that formed at methane seeps seem to only be found during the later 400 million years of Earth history,” says John Grotzinger, the Fletcher Jones Professor of Geology at Caltech and the principal investigator on the work described. “It is an interesting fact of the geologic record that, despite a well-preserved record of carbonates beginning 3.5 billion years ago, the first 3 billion years of Earth history does not record evidence of methane oxidation. This is a curious absence. We think it might be linked to changes in ocean chemistry through time, but more work needs to be done to explore that.”
Note: This story has been adapted from a news release issued by the California Institute of Technology
This diagram shows the March 11 fault motion sequence. 1. Rupture of the fault plane begins at the epicenter. 2. Rupture travels westward, down the fault plane towards Honshu. The island suffers violent shaking for 40 seconds. 3. The upward sloping east side of the fault plane begins to rupture, continuing for 30 to 35 seconds. The sediments overlying the east side expand up the fault plane in response to the force of the rupture. 4. The water above the sediments is pushed into an unstable dome that then flows out in all directions as a tsunami. – Anna Cobb, Stanford News Service
The magnitude 9 earthquake and resulting tsunami that struck Japan on March 11 were like a one-two punch – first violently shaking, then swamping the islands – causing tens of thousands of deaths and hundreds of billions of dollars in damage. Now Stanford researchers have discovered the catastrophe was caused by a sequence of unusual geologic events never before seen so clearly.
“It was not appreciated before this earthquake that this size of earthquake was possible on this plate boundary,” said Stanford geophysicist Greg Beroza. “It was thought that typical earthquakes were much smaller.”
The earthquake occurred in a subduction zone, where one great tectonic plate is being forced down under another tectonic plate and into the Earth’s interior along an active fault.
The fault on which the Tohoku-Oki earthquake took place slopes down from the ocean floor toward the west. It first ruptured mainly westward from its epicenter – 32 kilometers (about 20 miles) below the seafloor – toward Japan, shaking the island of Honshu violently for 40 seconds.
Surprisingly, the fault then ruptured eastward from the epicenter, up toward the ocean floor along the sloping fault plane for about 30 or 35 seconds.
As the rupture neared the seafloor, the movement of the fault grew rapidly, violently deforming the seafloor sediments sitting on top of the fault plane, punching the overlying water upward and triggering the tsunami.
“When the rupture approached the seafloor, it exploded into tremendously large slip,” said Beroza.”It displaced the seafloor dramatically.
“This amplification of slip near the surface was predicted in computer simulations of earthquake rupture, but this is the first time we have clearly seen it occur in a real earthquake.
“The depth of the water column there is also greater than elsewhere,” Beroza said. “That, together with the slip being greatest where the fault meets the ocean floor, led to the tsunami being outlandishly big.”
Beroza is one of the authors of a paper detailing the research, published online last week in Science Express.
“Now that this slip amplification has been observed in the Tohoku-Oki earthquake, what we need to figure out is whether similar earthquakes – and large tsunamis – could happen in other subduction zones around the world,” he said.
Beroza said the sort of “two-faced” rupture seen in the Tohoku-Oki earthquake has not been seen in other subduction zones, but that could be a function of the limited amount of data available for analyzing other earthquakes.
There is a denser network of seismometers in Japan than any other place in the world, he said. The sensors provided researchers with much more detailed data than is normally available after an earthquake, enabling them to discern the different phases of the March 11 temblor with much greater resolution than usual.
Prior to the Tohoku-Oki earthquake, Beroza and Shuo Ma, who is now an assistant professor at San Diego State University, had been working on computer simulations of what might happen during an earthquake in just such a setting. Their simulations had generated similar “overshoot” of sediments overlying the upper part of the fault plane.
Following the Japanese earthquake, aftershocks as large as magnitude 6.5 slipped in the opposite direction to the main shock. This is a symptom of what is called “extreme dynamic overshoot” of the upper fault plane, Beroza said, with the overextended sediments on top of the fault plane slipping during the aftershocks back in the direction they came from.
“We didn’t really expect this to happen because we believe there is friction acting on the fault” that would prevent any rebound, he said. “Our interpretation is that it slipped so much that it sort of overdid it. And in adjusting during the aftershock sequence, it went back a bit.
“We don’t see these bizarre aftershocks on parts of the fault where the slip is less,” he said.
The damage from the March 11 earthquake was so extensive in part simply because the earthquake was so large. But the way it ruptured on the fault plane, in two stages, made the devastation greater than it might have been otherwise, Beroza said.
The deeper part of the fault plane, which sloped downward to the west, was bounded by dense, hard rock on each side. The rock transmitted the seismic waves very efficiently, maximizing the amount of shaking felt on the island of Honshu.
The shallower part of the fault surface, which slopes upward to the east and surfaces at the Japan Trench – where the overlying plate is warped downward by the motion of the descending plate – had massive slip. Unfortunately, this slip was ideally situated to efficiently generate the gigantic tsunami, with devastating consequences.
Note: This story has been adapted from a news release issued by the Stanford University
This is a black smoker from the Mariner vent site in the Pacific Ocean’s Eastern Lau Spreading Center. – University of Delaware
Similar to humans, the bacteria and tiny plants living in the ocean need iron for energy and growth. But their situation is quite different from ours–for one, they can’t turn to natural iron sources like leafy greens or red meat for a pick-me-up.
So, from where does their iron come?
New research results published in the current issue of the journal Nature Geoscience point to a source on the seafloor: minute particles of pyrite, or fool’s gold, from hydrothermal vents at the bottom of the ocean.
Scientists already knew the vents’ cloudy plumes, which spew forth from the earth’s interior, include pyrite particles, but thought they were solids that settled back on the ocean bottom.
Now, scientists at the University of Delaware and other institutions have shown the vents emit a significant amount of microscopic pyrite particles that have a diameter 1,000 times smaller than that of a human hair.
Because the nanoparticles are so small, they are dispersed into the ocean rather than falling to the sea floor.
Barbara Ransom, program director in the National Science Foundation’s (NSF) Division of Ocean Sciences, which funded the research, called the discovery “very exciting.”
“These particles have long residence times in the ocean and can travel long distances from their sources, forming a potentially important food source for life in the deep sea,” she said.
The project also received support from another NSF program, the Experimental Program to Stimulate Competitive Research, or EPSCOR.
The mineral pyrite, or iron pyrite, has a metallic luster and brass-yellow color that led to its nickname: fool’s gold. In fact, pyrite is sometimes found in association with small quantities of gold.
Scientist George Luther of the University of Delaware explained the importance of the lengthy amount of time pyrite exists suspended in its current form in the sea, also known as its residence time.
Pyrite, which consists of iron and sulfur as iron disulfide, does not rapidly react with oxygen in seawater to form oxidized iron, or “rust,” allowing it to stay intact and move throughout the ocean better than other forms of iron.
“As pyrite travels from the vents to the ocean interior and toward the surface ocean, it oxidizes gradually to release iron, which becomes available in areas where iron is depleted so that organisms can assimilate it, then grow,” Luther said.
“It’s an ongoing iron supplement for the ocean–much as multivitamins are for humans.”
Growth of tiny plants known as phytoplankton can affect atmospheric oxygen and carbon dioxide levels.
Much of the research was performed by scientist and lead author Mustafa Yucel of the Universite Pierre et Marie Curie in France, conducted while Yucel worked on a doctorate at the University of Delaware.
It involved scientific cruises to the South Pacific and East Pacific Rise using the manned deep-sea submersible Alvin and the remotely operated vehicle Jason, both operated by the Woods Hole Oceanographic Institution.
Note: This story has been adapted from a news release issued by the National Science Foundation
A convective ‘drip’ of lithosphere (blue) below the Colorado Plateau is due to delamination caused by rising, partially molten material from the asthenosphere (gold), as plotted by Rice University researchers and their colleagues and described in a new paper in the journal Nature. (Credit Levander Lab/Rice University)
A team of scientists led by Rice University has figured out why the Colorado Plateau – a 130,000-square-mile region that straddles Colorado, Utah, Arizona and New Mexico — is rising even while parts of its lower crust appear to be falling. The massive, tectonically stable region of the western United States has long puzzled geologists.
A paper published today in the journal Nature shows how magmatic material from the depths slowly rises to invade the lithosphere — Earth’s crust and strong uppermost mantle. This movement forces layers to peel away and sink, said lead author Alan Levander, professor and the Carey Croneis Chair in Geology at Rice University.
The invading asthenosphere is two-faced. Deep in the upper mantle, between about 60 and 185 miles down, it’s usually slightly less dense and much less viscous than the overlying mantle lithosphere of the tectonic plates; the plates there can move over its malleable surface.
But when the asthenosphere finds a means to, it can invade the lithosphere and erode it from the bottom up. The partially molten material expands and cools as it flows upward. It infiltrates the stronger lithosphere, where it solidifies and makes the brittle crust and uppermost mantle heavy enough to break away and sink. The buoyant asthenosphere then fills the space left above, where it expands and thus lifts the plateau.
Levander and his fellow researchers know this because they’ve seen evidence of the process from data gathered by the massive USArray seismic observatory, hundreds of observatory-quality seismographs deployed 45 miles apart in a mobile array that covers a north/south strip of the United States.
The seismographs were first deployed in the West in 2004 and are heading eastward in a 10-year process, with each seismograph station in place for a year and a half. Seismic images made by Rice that are analogous to medical ultrasounds were combined with images like CAT scans made by seismologists at the University of Oregon; the resulting images revealed a pronounced anomaly extending from the crust well into the mantle.
Levander said the combined Colorado Plateau images show the convective “drip” of the lithosphere just north of the Grand Canyon; the lithosphere is slowly sinking several hundred kilometers into the Earth. That process may have helped create the canyon itself, as lifting of the plateau over the last 6 million years defined the Colorado River’s route.
Levander said USArray has found similar downwellings in two other locations in the American West; this suggests the forces deforming the lower crust and uppermost mantle are widespread. In both other locations, the downwellings happened within the past 10 million years. “But under the Colorado Plateau, we have caught it in the act,” he said.
“We had to find a trigger to cause the lithosphere to become dense enough to fall off,” Levander said. The partially molten asthenosphere is “hot and somewhat buoyant, and if there’s a topographic gradient along the asthenosphere’s upper surface, as there is under the Colorado Plateau, the asthenosphere will flow with it and undergo a small amount ofdecompression melting as it rises.”
It melts enough, he said, to infiltrate the base of the lithosphere and solidify, “and it’s at such a depth that it freezes as a dense phase. The heat from the invading melts also reduces the viscosity of the mantle lithosphere, making it flow more readily. At some point, the base of the lithosphere exceeds the density of the asthenosphere underneath and starts to drip.”
Levander said the National Science Foundation-funded USArray is already providing a wealth of geologic data. “I have quite a few seismologist friends in Europe attempting to develop a EuroArray, one of whom said, ‘Well, it looks like you have a machine producing Nature and Science papers.’ Well, yes, we do,” he said. “We can now see things we never saw before.”
Note: This story has been adapted from a news release issued by the Rice University
This is summer sea ice off the coast of Devon Island in Nunavut, Canada in August 2008. – Alex Gardner
Melting glaciers and ice caps on Canadian Arctic islands play a much greater role in sea level rise than scientists previously thought, according to a new study led by a University of Michigan researcher.
The 550,000-square-mile Canadian Arctic Archipelago contains some 30,000 islands. Between 2004 and 2009, the region lost the equivalent of three-quarters of the water in Lake Erie, the study found. Warmer-than-usual temperatures in those years caused a rapid increase in the melting of glacier ice and snow, said Alex Gardner, a research fellow in the Department of Atmospheric, Oceanic and Space Sciences who led the project. The study is published online in Nature on April 20.
“This is a region that we previously didn’t think was contributing much to sea level rise,” Gardner said. “Now we realize that outside of Antarctica and Greenland, it was the largest contributor for the years 2007 through 2009. This area is highly sensitive and if temperatures continue to increase, we will see much more melting.”
Ninety-nine percent of all the world’s land ice is trapped in the massive ice sheets of Antarctica and Greenland. Despite their size, they currently only account for about half of the land-ice being lost to oceans.
This is partly because they are cold enough that ice only melts at their edges.
The other half of the ice melt adding to sea-level rise comes from smaller mountain glaciers and ice caps such as those in the Canadian Arctic, Alaska, and Patagonia. This study underscores the importance of these many smaller, often overlooked regions, Gardner said.
During the first three years of this study, from 2004 through 2006, the region lost an average of 7 cubic miles of water per year. That increased dramatically to 22 cubic miles of water—roughly 24 trillion gallons—per year during the latter part of the study. Over the entire six years, this added a total of 1 millimeter to the height of the world’s oceans. While that might not sound like much, Gardner says that small amounts can make big differences.
In this study, a one-degree increase in average air temperature resulted in 15 cubic miles of additional melting.
Because the study took place over just six years, however, the results don’t signify a trend.
“This is a big response to a small change in climate,” Gardner said. “If the warming continues and we start to see similar responses in other glaciated regions, I would say it’s worrisome, but right now we just don’t know if it will continue.”
The United Nations projects that the oceans will rise by a full meter by the end of century. This could have ramifications for tens of millions of people who live in coastal cities and low-lying areas across the globe.
Future tsunamis and storm surges, for example, would more easily overtop ocean barriers.
To conduct the study, researchers from an international array of institutions performed numerical simulations and then used two different satellite-based techniques to independently validate their model results. Through laser altimetry, they measured changes in the region’s elevation over time. And through a technique called “gravimetry,” they measured changes in the Earth’s gravitational field, which signified a redistribution of mass—a loss of mass for glaciers and ice caps.
Note: This story has been adapted from a news release issued by the University of Michigan
This image, based on variations in electrical conductivity of underground rock, shows the volcanic plume of partly molten rock that feeds the Yellowstone supervolcano. Yellow and red indicate higher conductivity, green and blue indicate lower conductivity. Made by University of Utah geophysicists and computer scientists, this is the first large-scale ‘geoelectric’ image of the Yellowstone hotspot. – University of Utah.
University of Utah geophysicists made the first large-scale picture of the electrical conductivity of the gigantic underground plume of hot and partly molten rock that feeds the Yellowstone supervolcano. The image suggests the plume is even bigger than it appears in earlier images made with earthquake waves.
“It’s like comparing ultrasound and MRI in the human body; they are different imaging technologies,” says geophysics Professor Michael Zhdanov, principal author of the new study and an expert on measuring magnetic and electrical fields on Earth’s surface to find oil, gas, minerals and geologic structures underground.
“It’s a totally new and different way of imaging and looking at the volcanic roots of Yellowstone,” says study co-author Robert B. Smith, professor emeritus and research professor of geophysics and a coordinating scientist of the Yellowstone Volcano Observatory.
The new University of Utah study has been accepted for publication in Geophysical Research Letters, which plans to publish it within the next few weeks.
In a December 2009 study, Smith used seismic waves from earthquakes to make the most detailed seismic images yet of the “hotspot” plumbing that feeds the Yellowstone volcano. Seismic waves move faster through cold rock and slower through hot rock. Measurements of seismic-wave speeds were used to make a three-dimensional picture, quite like X-rays are combined to make a medical CT scan.
The 2009 images showed the plume of hot and molten rock dips downward from Yellowstone at an angle of 60 degrees and extends 150 miles west-northwest to a point at least 410 miles under the Montana-Idaho border – as far as seismic imaging could “see.”
In the new study, images of the Yellowstone plume’s electrical conductivity – generated by molten silicate rocks and hot briny water mixed in partly molten rock – shows the conductive part of the plume dipping more gently, at an angle of perhaps 40 degrees to the west, and extending perhaps 400 miles from east to west. The geoelectric image can “see” only 200 miles deep.
Two Views of the Yellowstone Volcanic Plume
Smith says the geoelectric and seismic images of the Yellowstone plume look somewhat different because “we are imaging slightly different things.” Seismic images highlight materials such as molten or partly molten rock that slow seismic waves, while the geoelectric image is sensitive to briny fluids that conduct electricity.
“It [the plume] is very conductive compared with the rock around it,” Zhdanov says. “It’s close to seawater in conductivity.”
The lesser tilt of the geoelectric plume image raises the possibility that the seismically imaged plume, shaped somewhat like a tilted tornado, may be enveloped by a broader, underground sheath of partly molten rock and liquids, Zhdanov and Smith say.
“It’s a bigger size” in the geoelectric picture, says Smith. “We can infer there are more fluids” than shown by seismic images.
Despite differences, he says, “this body that conducts electricity is in about the same location with similar geometry as the seismically imaged Yellowstone plume.”
Zhdanov says that last year, other researchers presented preliminary findings at a meeting comparing electrical and seismic features under the Yellowstone area, but only to shallow depths and over a smaller area.
The study was conducted by Zhdanov, Smith, two members of Zhdanov’s lab – research geophysicist Alexander Gribenko and geophysics Ph.D. student Marie Green – and computer scientist Martin Cuma of the University of Utah’s Center for High Performance Computing. Funding came from the National Science Foundation (NSF) and the Consortium for Electromagnetic Modeling and Inversion, which Zhdanov heads.
The Yellowstone Hotspot at a Glance
The new study says nothing about the chances of another cataclysmic caldera (giant crater) eruption at Yellowstone, which has produced three such catastrophes in the past 2 million years.
Almost 17 million years ago, the plume of hot and partly molten rock known as the Yellowstone hotspot first erupted near what is now the Oregon-Idaho-Nevada border. As North America drifted slowly southwest over the hotspot, there were more than 140 gargantuan caldera eruptions – the largest kind of eruption known on Earth – along a northeast-trending path that is now Idaho’s Snake River Plain.
The hotspot finally reached Yellowstone about 2 million years ago, yielding three huge caldera eruptions about 2 million, 1.3 million and 642,000 years ago. Two of the eruptions blanketed half of North America with volcanic ash, producing 2,500 times and 1,000 times more ash, respectively, than the 1980 eruption of Mount St. Helens in Washington state. Smaller eruptions occurred at Yellowstone in between the big blasts and as recently as 70,000 years ago.
Seismic and ground-deformation studies previously showed the top of the rising volcanic plume flattens out like a 300-mile-wide pancake 50 miles beneath Yellowstone. There, giant blobs of hot and partly molten rock break off the top of the plume and slowly rise to feed the magma chamber – a spongy, banana-shaped body of molten and partly molten rock located about 4 miles to 10 miles beneath the ground at Yellowstone.
Computing a Geoelectrical Image of Yellowstone’s Hotspot Plume
Zhdanov and colleagues used data collected by EarthScope, an NSF-funded effort to collect seismic, magnetotelluric and geodetic (ground deformation) data to study the structure and evolution of North America. Using the data to image the Yellowstone plume was a computing challenge because so much data was involved.
Inversion is a formal mathematical method used to “extract information about the deep geological structures of the Earth from the magnetic and electrical fields recorded on the ground surface,” Zhdanov says. Inversion also is used to convert measurements of seismic waves at the surface into underground images.
Magnetotelluric measurements record very low frequencies of electromagnetic radiation – about 0.0001 to 0.0664 Hertz – far below the frequencies of radio or TV signals or even electric power lines. This low-frequency, long-wavelength electromagnetic field penetrates a couple hundred miles into the Earth. By comparison, TV and radio waves penetrate only a fraction of an inch.
The EarthScope data were collected by 115 stations in Wyoming, Montana and Idaho – the three states straddled by Yellowstone National Park. The stations, which include electric and magnetic field sensors, are operated by Oregon State University for the Incorporated Research Institutions for Seismology, a consortium of universities.
In a supercomputer, a simulation predicts expected electric and magnetic measurements at the surface based on known underground structures. That allows the real surface measurements to be “inverted” to make an image of underground structure.
Zhdanov says it took about 18 hours of supercomputer time to do all the calculations needed to produce the geoelectric plume picture. The supercomputer was the Ember cluster at the University of Utah’s Center for High Performance Computing, says Cuma, the computer scientist.
Ember has 260 nodes, each with 12 CPU (central processing unit) cores, compared with two to four cores commonly found on personal computer, Cuma says. Of the 260 nodes, 64 were used for the Yellowstone study, which he adds is “roughly equivalent to 200 common PCs.”
To create the geoelectric image of Yellowstone’s plume required 2 million pixels, or picture elements.
Note: This story has been adapted from a news release issued by the University of Utah
Wildlife Conservation Society scientists working in Afghanistan recently discovered one of the largest natural stone arches in the world. – Ayub Alavi
Researchers from the Wildlife Conservation Society have stumbled upon a geological colossus in a remote corner of Afghanistan: a natural stone arch spanning more than 200 feet across its base.
Located at the central highlands of Afghanistan, the recently discovered Hazarchishma Natural Bridge is more than 3,000 meters (nearly 10,000 feet) above sea level, making it one of the highest large natural bridges in the world. It also ranks among the largest such structures known.
“It’s one of the most spectacular discoveries ever made in this region,” said Joe Walston, Director of the Wildlife Conservation Society’s Asia Program. “The arch is emblematic of the natural marvels that still await discovery in Afghanistan.”
Wildlife Conservation Society staff Christopher Shank and Ayub Alavi discovered the massive arch in late 2010 in the course of surveying the northern edge of the Bamyan plateau for wildlife (the landscape is home to ibex and urial wild sheep) and visiting local communities.
After making the discovery, they returned to the Hazarchishma Natural Bridge (named after a nearby village) in February 2011 to take accurate measure of the natural wonder. The total span of arch-the measurement by which natural bridges are ranked-is 210.6 feet in width, making it the 12th largest natural bridge in the world. This finding pushes Utah’s Outlaw Arch in Dinosaur National Monument-smaller than Hazarchishma by more than four feet-to number 13 on the list.
The world’s largest natural arch-Fairy Bridge-is located by Buliu River in Guangxi, China, and spans a staggering 400 feet in width. Several of the top 20 largest natural arches are located in the state of Utah in the U.S.
Consisting of rock layers formed between the Jurassic Period (200-145 million years ago) and the more recent Eocene Epoch (55-34 million years ago), the Hazarchishma Natural Bridge was carved over millennia by the once flowing waters of the now dry Jawzari Canyon.
With the assistance of WCS and support from USAID (United States Agency for International Development), the government of Afghanistan has launched several initiatives to safeguard the country’s wild places and the wildlife they contain. In 2009, the government gazetted the country’s first national park, Band-e-Amir, approximately 100 kilometers south of Hazarchishma Natural Bridge. The park was established with technical assistance from WCS’s Afghanistan Program. WCS also worked with Afghanistan’s National Environment Protection Agency (NEPA) in producing the country’s first-ever list of protected species, an action that now bans the hunting of snow leopards, wolves, brown bears, and other species. In a related effort, WCS now works to limit illegal wildlife trade in the country through educational workshops for soldiers at Bagram Air Base and other military bases across Afghanistan. WCS also works with more than 55 local communities in Afghanistan to better manage their natural resources, helping them conserve wildlife while improving their livelihoods.
“Afghanistan has taken great strides in initiating programs to preserve the country’s most beautiful wild places as well as conserve its natural resources,” said Peter Zahler, Deputy Director for the WCS Asia Program. “This newfound marvel adds to the country’s growing list of natural wonders and economic assets.”
Note: This story has been adapted from a news release issued by the Wildlife Conservation Society
This images shows bands of glowing magma from submarine volcano. – NOAA/National Science Foundation
Between 75 and 80 per cent of all volcanic activity on Earth takes place at deep-sea, mid-ocean ridges. Most of these volcanoes produce effusive lava flows rather than explosive eruptions, both because the levels of magmatic gas (which fuel the explosions and are made up of a variety of components, including, most importantly CO2) tend to be low, and because the volcanoes are under a lot of pressure from the surrounding water.
Over about the last 10 years however, geologists have nevertheless speculated, based on the presence of volcanic ash in certain sites, that explosive eruptions can also occur in deep-sea volcanoes.
But no one has been able to prove it until now.
By using an ion microprobe, Christoph Helo, a PhD student in McGill’s Department of Earth and Planetary Sciences, has now discovered very high concentrations of CO2 in droplets of magma trapped within crystals recovered from volcanic ash deposits on Axial Volcano on the Juan de Fuca Ridge, off the coast of Oregon.
These entrapped droplets represent the state of the magma prior to eruption. As a result, Helo and fellow researchers from McGill, the Monterey Bay Aquarium Research Institute, and the Woods Hole
Oceanographic Institution, have been able to prove that explosive eruptions can indeed occur in deep-sea volcanoes. Their work also shows that the release of CO2 from the deeper mantle to the Earth’s atmosphere, at least in certain parts of mid-ocean ridges, is much higher than had previously been imagined.
Given that mid-ocean ridges constitute the largest volcanic system on Earth, this discovery has important implications for the global carbon cycle which have yet to be explored.
Note: This story has been adapted from a news release issued by the McGill University
The images show the progression of damage to the Fukushima Dai-ichi Nuclear Power Plant from March 12 to March 17. – Analysis by RIT Digital Imaging and Remote Sensing Laboratory within the Chester F. Carlson Center for Imaging Science.
Japan needs maps. Not just any kind-detailed informational maps georegistered with latitude and longitude and annotated with simple, self-evident details: this bridge is out, this port is damaged, this farm field is scoured; this one is verdant.
Researchers at Rochester Institute of Technology are processing satellite imagery of regions in Japan affected by the 9.0 magnitude earthquake and tsunami that devastated sections of the country’s east coast on March 11. The U.S. Geological Survey, a member of the International Charter “Space and Major Disasters,” organized the volunteer effort involving about 10 organizations, including Harvard University, George Mason University, Penn State and the Jet Propulsion Laboratory.
RIT signed on to process images of the Fukushima Nuclear Power Plant and the cities of Hachinohe and Kesennuma. At the request of the Japanese, scientists at RIT created before-and-after images that can be printed on large sheets of paper. The team uploads 30 megabyte PDFs to the U.S. Geological Survey’s website for charter members and Japanese emergency responders to access.
“Once we upload it, it’s out of our hands,” says David Messinger, associate research professor and director of the Digital Imaging Remote Sensing Laboratory in RIT’s Chester F. Carlson Center for Imaging Science. “If you have the electronic version, you can make measurements on it,” he says. “The assumption is they want the big format so they can print it out, roll it up and take it into the field.”
The Japanese relief workers requested high-resolution images of the Fukushima Nuclear Power Plant. The RIT team processed imagery looking down into the reactors and the containment shells on March 12, the day after the earthquake and tsunami hit and prior to the explosions at the plant. High-resolution image-maps from March 18 show extensive damage and a smoldering reactor.
“We were tasked with the nuke plant Friday [March 18] morning and we uploaded it about 6 that night,” says Don McKeown, distinguished researcher in the Carlson Center for Imaging Science.
The 13-hour time difference has made the workflow difficult, Messinger notes. “While we’re doing this here, it’s the middle of the night there, so the feedback loops are slow.
“We were pushing hard,” he adds. “We wanted to get maps to them before their morning work shift started.”
They are mapping the area around the power plant as well, processing imagery from a broader view of the terrain used as farmland.
“We have a large image of Fukushima,” McKeown adds. “We’re committed to making a big map of this area. This is a very agricultural region and there are restrictions about food coming out of the area.”
The RIT team, led by McKeown and Messinger, includes graduate students Sanjit Maitra and Weihua “Wayne” Sun in the Center for Imaging Science and staff members Steve Cavilia, Chris DiAngelis, Jason Faulring and Nina Raqueño. They created the maps using imagery from WorldView 1 and WorldView 2 satellites operated by Digital Globe, a member of RIT’s Information Products Laboratory for Emergency Response (IPLER), and GeoEye 1, a high-resolution commercial satellite operated by GeoEye Inc.
“This really fits what IPLER is all about-information products,” McKeown says.
RIT and the University at Buffalo formed IPLER six months before the earthquake struck Haiti in January 2010. Connections with industry partners led RIT to capture and process multispectral and LIDAR images of Port-au-Prince and surrounding towns for the World Bank.
“With Haiti, we learned how, in a disaster, to send an imaging instrument into the field, collect the relevant data, get it back to campus and do the right processing to the imagery,” Messinger says. “In this case, we’re learning how to take imagery that we didn’t collect and produce the actual product that will be delivered to the first responders in the field in a very short time frame. We’ve learned a lot about the second phase of the process now.”
Note: This story has been adapted from a news release issued by the Rochester Institute of Technology
Sediment samples in the lab of Richard Norris obtained by the Ocean Drilling Program reveal the mark of ‘hyperthermals,’ warming events lasting thousands of years that changed the composition of the sediment and its color. The packaged sediment sample on the left contains sediment formed in the wake of a 55-million-year-old warming event and the sample on the right is sediment from a later era after global temperatures stabilized. – Scripps Institution of Oceanography, UC San Diego
Bursts of intense global warming that have lasted tens of thousands of years have taken place more frequently throughout history than previously believe, according to evidence gathered by a team led by Scripps Institution of Oceanography, UC San Diego researchers.
Richard Norris, a professor of geology at Scripps who co-authored the report, said that releases of carbon dioxide sequestered in the deep oceans were the most likely trigger of these ancient “hyperthermal” events. Most of the events raised average global temperatures between 2° and 3° Celsius (3.6 and 5.4° F), an amount comparable to current conservative estimates of how much temperatures are expected to rise in coming decades as a consequence of anthropogenic global warming. Most hyperthermals lasted about 40,000 years before temperatures returned to normal.
The study appears in the March 17 issue of the journal Nature.
“These hyperthermals seem not to have been rare events,” Norris said, “hence there are lots of ancient examples of global warming on a scale broadly like the expected future warming. We can use these events to examine the impact of global change on marine ecosystems, climate and ocean circulation.”
The hyperthermals took place roughly every 400,000 years during a warm period of Earth history that prevailed some 50 million years ago. The strongest of them coincided with an event known as the Paleocene-Eocene Thermal Maximum, the transition between two geologic epochs in which global temperatures rose between 4° and 7° C (7.2° and 12.6° F) and needed 200,000 years to return to historical norms. The events stopped taking place around 40 million years ago, when the planet entered a cooling phase. No warming events of the magnitude of these hyperthermals have been detected in the geological record since then.
Phil Sexton, a former student of Norris’ now at the Open University in the United Kingdom, led the analysis of sediment cores collected off the South American coast. In the cores, evidence of the warm periods presented itself in bands of gray sediment layered within otherwise pale greenish mud. The gray sediment contained increased amounts of clay left after the calcareous shells of microscopic organisms were dissolved on the sea floor. These clay-rich intervals are consistent with ocean acidification episodes that would have been triggered by large-scale releases of carbon dioxide. Large influxes of carbon dioxide change the chemistry of seawater by producing greater amounts of carbonic acid in the oceans.
The authors concluded that a release of carbon dioxide from the deep oceans was a more likely cause of the hyperthermals than other triggering events that have been hypothesized. The regularity of the hyperthermals and relatively warm ocean temperatures of the period makes them less likely to have been caused by events such as large melt-offs of methane hydrates, terrestrial burning of peat or even proposed cometary impacts. The hyperthermals could have been set in motion by a build-up of carbon dioxide in the deep oceans caused by slowing or stopping of circulation in ocean basins that prevented carbon dioxide release.
Norris noted that the hyperthermals provide historical perspective on what Earth will experience as it continues to warm from widespread use of fossil fuels, which has increased carbon dioxide concentrations in the atmosphere nearly 50 percent since the beginning of the Industrial Revolution. Hyperthermals can help scientists produce a range of estimates for how long it will take for temperatures to fully revert to historical norms depending on how much warming human activities cause.
“In 100 to 300 years, we could produce a signal on Earth that takes tens of thousands of years to equilibrate, judging from the geologic record,” he said.
The scientists hope to better understand how fast the conditions that set off hyperthermals developed. Norris said that 50 million year old sediments in the North Sea are finely layered enough for scientists to distinguish decade-to-decade or even year-to-year changes.
Note: This story has been adapted from a news release issued by the University of California – San Diego
Quartz may play a major role in the movements of continents, known as plate tectonics. – USG
More than 40 years ago, pioneering tectonic geophysicist J. Tuzo Wilson published a paper in the journal Nature describing how ocean basins opened and closed along North America’s eastern seaboard.
His observations, dubbed “The Wilson Tectonic Cycle,” suggested the process occurred many times during Earth’s long history, most recently causing the giant supercontinent Pangaea to split into today’s seven continents.
Wilson’s ideas were central to the so-called Plate Tectonic Revolution, the foundation of contemporary theories for processes underlying mountain-building and earthquakes.
Since his 1967 paper, additional studies have confirmed that large-scale deformation of continents repeatedly occurs in some regions but not others, though the reasons why remain poorly understood.
Now, new findings by Utah State University geophysicist Tony Lowry and colleague Marta Pérez-Gussinyé of Royal Holloway, University of London, shed surprising light on these restless rock cycles.
“It all begins with quartz,” says Lowry, who published results of the team’s recent study in the March 17 issue of Nature.
The scientists describe a new approach to measuring properties of the deep crust.
It reveals quartz’s key role in initiating the churning chain of events that cause Earth’s surface to crack, wrinkle, fold and stretch into mountains, plains and valleys.
“If you’ve ever traveled westward from the Midwest’s Great Plains toward the Rocky Mountains, you may have wondered why the flat plains suddenly rise into steep peaks at a particular spot,” Lowry says.
“It turns out that the crust beneath the plains has almost no quartz in it, whereas the Rockies are very quartz-rich.”
He thinks that those belts of quartz could be the catalyst that sets the mountain-building rock cycle in motion.
“Earthquakes, mountain-building and other expressions of continental tectonics depend on how rocks flow in response to stress,” says Lowry.
“We know that tectonics is a response to the effects of gravity, but we know less about rock flow properties and how they change from one location to another.”
Wilson’s theories provide an important clue, Lowry says, as scientists have long observed that mountain belts and rift zones have formed again and again at the same locations over long periods of time.
But why?
“Over the last few decades, we’ve learned that high temperatures, water and abundant quartz are all critical factors in making rocks flow more easily,” Lowry says. “Until now, we haven’t had the tools to measure these factors and answer long-standing questions.”
Since 2002, the National Science Foundation (NSF)-funded Earthscope Transportable Array of seismic stations across the western United States has provided remote sensing data about the continent’s rock properties.
“We’ve combined Earthscope data with other geophysical measurements of gravity and surface heat flow in an entirely new way, one that allows us to separate the effects of temperature, water and quartz in the crust,” Lowry says.
Earthscope measurements enabled the team to estimate the thickness, along with the seismic velocity ratio, of continental crust in the American West.
“This intriguing study provides new insights into the processes driving large-scale continental deformation and dynamics,” says Greg Anderson, NSF program director for EarthScope. “These are key to understanding the assembly and evolution of continents.”
Seismic velocity describes how quickly sound waves and shear waves travel through rock, offering clues to its temperature and composition.
“Seismic velocities are sensitive to both temperature and rock type,” Lowry says.
“But if the velocities are combined as a ratio, the temperature dependence drops out. We found that the velocity ratio was especially sensitive to quartz abundance.”
Even after separating out the effects of temperature, the scientists found that a low seismic velocity ratio, indicating weak, quartz-rich crust, systematically occurred in the same place as high lower-crustal temperatures modeled independently from surface heat flow.
“That was a surprise,” he says. “We think this indicates a feedback cycle, where quartz starts the ball rolling.”
If temperature and water are the same, Lowry says, rock flow will focus where the quartz is located because that’s the only weak link.
Once the flow starts, the movement of rock carries heat with it and that efficient movement of heat raises temperature, resulting in weakening of crust.
“Rock, when it warms up, is forced to release water that’s otherwise chemically bound in crystals,” he says.
Water further weakens the crust, which increasingly focuses the deformation in a specific area.
Note: This story has been adapted from a news release issued by the National Science Foundation
An assessment of coastal change over the past 150 years has found 68 percent of beaches in the New England and Mid-Atlantic region are eroding, according to a new US Geological Survey report. Scientists studied 650 miles of the New England and Mid-Atlantic coasts and found the average rate of coastal change was negative 1.6 feet per year. Of those beaches eroding,the most extreme case exceeded 60 feet per year.
An assessment of coastal change over the past 150 years has found 68 percent of beaches in the New England and Mid-Atlantic region are eroding, according to a U.S. Geological Survey report released today.
Scientists studied more than 650 miles of the New England and Mid-Atlantic coasts and found the average rate of coastal change – taking into account beaches that are both eroding and prograding — was negative 1.6 feet per year. Of those beaches eroding, the most extreme case exceeded 60 feet per year.
The past 25 to 30 years saw a small reduction in the percentage of beaches eroding – dropping to 60 percent, possibly as a result of beach restoration activities such as adding sand to beaches.
“This report provides invaluable objective data to help scientists and managers better understand natural changes to and human impacts on the New England and Mid-Atlantic coasts,” said Anne Castle, Assistant Secretary of the Interior for Water and Science. “The information gathered can inform decisions about future land use, transportation corridors, and restoration projects.”
Beaches change in response to a variety of factors, including changes in the amount of available sand, storms, sea-level rise and human activities. How much a beach is eroding or prograding in any given location is due to some combination of these factors, which vary from place to place.
The Mid-Atlantic coast – from Long Island, N.Y. to the Virginia-North Carolina border — is eroding at higher average rates than the New England coast. The difference in the type of coastline, with sandy areas being more vulnerable to erosion than areas with a greater concentration of rocky coasts, was the primary factor.
The researchers found that, although coastal change is highly variable, the majority of the coast is eroding throughout both regions, indicating erosion hazards are widespread.
“There is increasing need for this kind of comprehensive assessment in all coastal environments to guide managed response to sea-level rise,” said Dr. Cheryl Hapke of the USGS, lead author of the new report. “It is very difficult to predict what may happen in the future without a solid understanding of what has happened in the past.”
The researchers used historical data sources such as maps and aerial photographs, as well as modern data like lidar, or “light detection and ranging,” to measure shoreline change at more than 21,000 locations.
This analysis of past and present trends of shoreline movement is designed to allow for future repeatable analyses of shoreline movement, coastal erosion, and land loss. The results of the study provide a baseline for coastal change information that can be used to inform a wide variety of coastal management decisions, Hapke said.
The report, titled “National Assessment of Shoreline Change: Historical Shoreline Change along the New England and Mid-Atlantic Coasts,” is the fifth report produced as part of the USGS’s National Assessment of Shoreline Change project. An accompanying report that provides the geographic information system (GIS) data used to conduct the coastal change analysis is being released simultaneously.
Note: This story has been adapted from a news release issued by the United States Geological Survey
Like a string of underwater pearls, the Louisville Seamount Trail is strung across the Pacific. – IODP
Nearly half a mile of rock retrieved from beneath the seafloor is yielding new clues about how underwater volcanoes are created and whether the hotspots that led to their formation have moved over time.
Geoscientists have just completed an expedition to a string of underwater volcanoes, or seamounts, in the Pacific Ocean known as the Louisville Seamount Trail.
There they collected samples of sediments, basalt lava flows and other volcanic eruption materials to piece together the history of this ancient trail of volcanoes.
The expedition was part of the Integrated Ocean Drilling Program (IODP).
“Finding out whether hotspots in Earth’s mantle are stationary or not will lead to new knowledge about the basic workings of our planet,” says Rodey Batiza, section head for marine geosciences in the National Science Foundation’s (NSF) Division of Ocean Sciences.
Tens of thousands of seamounts exist in the Pacific Ocean. Expedition scientists probed a handful of the most important of these underwater volcanoes.
“We sampled ancient lava flows, and a fossilized algal reef,” says Anthony Koppers of Oregon State University. “The samples will be used to study the construction and evolution of individual volcanoes.”
Koppers led the expedition aboard the scientific research vessel JOIDES Resolution, along with co-chief scientist Toshitsugu Yamazaki from the Geological Survey of Japan at the National Institute of Advanced Industrial Science and Technology.
IODP is supported by NSF and Japan’s Ministry of Education, Culture, Sports, Science and Technology.
Over the last two months, scientists drilled 1,113 meters (3,651 feet) into the seafloor to recover 806 meters (2,644 feet) of volcanic rock.
The samples were retrieved from six sites at five seamounts ranging in age from 50 to 80 million years old.
“The sample recovery during this expedition was truly exceptional. I believe we broke the record for drilling igneous rock with a rotary core barrel,” says Yamazaki.
Igneous rock is rock formed through the cooling and solidification of magma or lava, while a rotary core barrel is a type of drilling tool used for penetrating hard rocks.
Trails of volcanoes found in the middle of tectonic plates, such as the Hawaii-Emperor and Louisville Seamount Trails, are believed to form from hotspots–plumes of hot material found deep within the Earth that supply a steady stream of heated rock.
As a tectonic plate drifts over a hotspot, new volcanoes are formed and old ones become extinct. Over time, a trail of volcanoes is formed. The Louisville Seamount Trail is some 4,300 kilometers (about 2,600 miles) long.
“Submarine volcanic trails like the Louisville Seamount Trail are unique because they record the direction and speed at which tectonic plates move,” says Koppers.
Scientists use these volcanoes to study the motion of tectonic plates, comparing the ages of the volcanoes against their location over time to calculate the rate at which a plate moved over a hotspot.
These calculations assume the hotspot stays in the same place.
“The challenge,” says Koppers, “is that no one knows if hotspots are truly stationary or if they somehow wander over time. If they wander, then our calculations of plate direction and speed need to be re-evaluated.”
“More importantly,” he says, “the results of this expedition will give us a more accurate picture of the dynamic nature of the interior of the Earth on a planetary scale.”
Recent studies in Hawaii have shown that the Hawaii hotspot may have moved as much as 15 degrees latitude (about 1,600 kilometers or 1,000 miles) over a period of 30 million years.
“We want to know if the Louisville hotspot moved at the same time and in the same direction as the Hawaiian hotspot. Our models suggest that it’s the opposite, but we won’t really know until we analyze the samples from this expedition,” says Yamazaki.
In addition to the volcanic rock, the scientists also recovered sedimentary rocks that preserve shells and an ancient algal reef, typical of living conditions in a very shallow marine environment.
These ancient materials show that the Louisville seamounts were once an archipelago of volcanic islands.
“We were really surprised to find only a thin layer of sediments on the tops of the seamounts, and only very few indications for the eruption of lava flows above sea level,” says Koppers.
The IODP Louisville Seamount Trail Expedition wasn’t solely focused on geology.
More than 60 samples from five seamounts were obtained for microbiology research.
Exploration of microbial communities under the seafloor, known as the “subseafloor biosphere,” is a rapidly developing field of research.
Using the Louisville samples, microbiologists will study both living microbial residents and those that were abundant over a large area, but now occupy only a few small areas.
They will examine population differences in microbes in the volcanic rock and overlying sediments, and in different kinds of lava flows.
They will also look for population patterns at various depths in the seafloor and compare them with seamounts of varying ages.
Samples from the Louisville Seamount Trail expedition will be analyzed to determine their age, composition and magnetic properties.
The information will be pieced together like a puzzle to create a story of the eruption history of the Louisville volcanoes.
It will then be compared to that of the Hawaiian volcanoes to determine whether hotspots are on the move.
The IODP is an international research program dedicated to advancing scientific understanding of the Earth through drilling, coring and monitoring the subseafloor.
Note: This story has been adapted from a news release issued by the National Science Foundation
To measure the Earth’s magnetic field, an orange laser beam is directed at a layer of sodium 90 kilometers above the Earth. The beam is pulsed at a rate determined by the local magnetic field in order to excite spin polarization of the sodium atoms. The fluorescent emission from the sodium, which depends on the spin polarization, is detected by a ground-based telescope and analyzed to determine the strength of the magnetic field. – Dmitry Budker lab/UC Berkeley
Mapping the Earth’s magnetic field – to find oil, track storms or probe the planet’s interior – typically requires expensive satellites.
University of California, Berkeley, physicists have now come up with a much cheaper way to measure the Earth’s magnetic field using only a ground-based laser.
The method involves exciting sodium atoms in a layer 90 kilometers above the surface and measuring the light they give off.
“Normally, the laser makes the sodium atom fluoresce,” said Dmitry Budker, UC Berkeley professor of physics. “But if you modulate the laser light, when the modulation frequency matches the spin precession of the sodium atoms, the brightness of the spot changes.”
Because the local magnetic field determines the frequency at which the atoms precess, this allows someone with a ground-based laser to map the magnetic field anywhere on Earth.
Budker and three current and former members of his laboratory, as well as colleagues with the European Southern Observatory (ESO), lay out their technique in a paper appearing online this week in the journal Proceedings of the National Academy of Sciences.
Various satellites, ranging from the Geostationary Operational Environmental Satellites, or GOES, to an upcoming European mission called SWARM, carry instruments to measure the Earth’s magnetic field, providing data to companies searching for oil or minerals, climatologists tracking currents in the atmosphere and oceans, geophysicists studying the planet’s interior and scientists tracking space weather.
Ground-based measurements, however, can avoid several problems associated with satellites, Budker said. Because these spacecraft are moving at high speed, it’s not always possible to tell whether a fluctuation in the magnetic field strength is real or a result of the spacecraft having moved to a new location. Also, metal and electronic instruments aboard the craft can affect magnetic field measurements.
“A ground-based remote sensing system allows you to measure when and where you want and avoids problems of spatial and temporal dependence caused by satellite movement,” he said. “Initially, this is going to be competitive with the best satellite measurements, but it could be improved drastically.”
Laser guide stars
The idea was sparked by a discussion Budker had with a colleague about of the lasers used by many modern telescopes to remove the twinkle from stars caused by atmospheric disturbance. That technique, called laser guide star adaptive optics, employs lasers to excite sodium atoms deposited in the upper atmosphere by meteorites. Once excited, the atoms fluoresce, emitting light that mimics a real star.
Telescopes with such a laser guide star, including the Very Large Telescope in Chile and the Keck telescopes in Hawaii, adjust their “rubber mirrors” to cancel the laser guide star’s jiggle, and thus remove the jiggle for all nearby stars.
It is well known that these sodium atoms are affected by the Earth’s magnetic field. Budker, who specializes in extremely precise magnetic-field measurements, realized that you could easily determine the local magnetic field by exciting the atoms with a pulsed or modulated laser of the type used in guide stars. The method is based on the fact that the electron spin of each sodium atom precesses like a top in the presence of a magnetic field. Hitting the atom with light pulses at just the right frequency will cause the electrons to flip, affecting the way the atoms interact with light.
“It suddenly struck me that what we do in my lab with atomic magnetometers we can do with atoms freely floating in the sky,” he said.
Budker’s former post-doctoral fellow James Higbienow an assistant professor of physics and astronomy at Bucknell University – conducted laboratory measurements and computer simulations confirming that the effects of a modulated laser could be detected from the ground by a small telescope. He was assisted by Simon M. Rochester, who received his Ph.D. in physics from UC Berkeley last year, and current post-doctoral fellow Brian Patton.
Portable laser magnetometers
In practice, a 20- to 50-watt laser small enough to load on a truck or be attuned to the orange sodium line (589 nanometer wavelength) would shine polarized light into the 10 kilometer-thick sodium layer in the mesosphere, which is about 90 kilometers overhead. The frequency with which the laser light is modulated or pulsed would be shifted slightly around this wavelength to stimulate a spin flip.
The decrease or increase in brightness when the modulation is tuned to a “sweet spot” determined by the magnitude of the magnetic field could be as much as 10 percent of the typical fluorescence, Budker said. The spot itself would be too faint to see with the naked eye, but the brightness change could easily be measured by a small telescope.
“This is such a simple idea, I thought somebody must have thought of it before,” Budker said.
He was right. William Happer, a physicist who pioneered spin-polarized spectroscopy and the sodium laser guide stars, had thought of the idea, but had never published it.
“I was very, very happy to hear that, because I felt there may be a flaw in the idea, or that it had already been published,” Budker said.
While Budker’s lab continues its studies of how spin-polarized sodium atoms emit and absorb light, Budker’s co-authors Ronald Holzlöhner and Domenico Bonaccini Calia of the ESO in Garching, Germany, are building a 20-watt modulated laser for the Very Large Array in Chile that can be used to test the theory.
Note: This story has been adapted from a news release issued by the University of California – Berkeley
These maps show the rate at which the ice sheet over the British Isles during the last Ice Age melted. The ka on the images is short for thousand years and BP is ‘before present.’ So 27 Ka BP is the map of the ice sheet at 27,000 years ago. – University of Sheffiel
A set of maps created by the University of Sheffield have illustrated, for the first time, how our last British ice sheet shrunk during the Ice Age.
Led by Professor Chris Clark from the University’s Department of Geography, a team of experts developed the maps to understand what effect the current shrinking of ice sheets in parts of the Antarctic and Greenland will have on the speed of sea level rise.
The unique maps record the pattern and speed of shrinkage of the large ice sheet that covered the British Isles during the last Ice Age, approximately 20,000 years ago. The sheet, which subsumed most of Britain, Ireland and the North Sea, had an ice volume sufficient to raise global sea level by around 2.5 metres when it melted.
Using the maps, researchers will be able to understand the mechanisms and rate of change of ice sheet retreat, allowing them to make predictions for our polar regions, whose ice sheets appear to be melting as a result of temperature increases in the air and oceans.
The maps are based on new information on glacial landforms, such as moraines and drumlins, which were discovered using new technology such as remote sensing data that is able to image the land surface and seafloor at unprecedented resolutions. Experts combined this new information with that from fieldwork, some of it dating back to the nineteenth century, to produce the final maps of retreat.
It is also possible to use the maps to reveal exactly when land became exposed from beneath the ice and was available for colonization and use by plants, animals and humans. This provides the opportunity for viewers to pinpoint when their town/region emerged.
Professor Chris Clark, from the University of Sheffield’s Department of Geography, said: “It took us over 10 years to gather all the information in order to produce these maps, and we are delighted with the results, It is great to be able to visualize the ice sheet and notice that retreat speeds up and slows down, and it is vital of course that we learn exactly why. With such understanding we will be able to better predict ice losses in Greenland and Antarctica.
“In our next phase of work we hope to really tighten up on the timing and rates of retreat in more detail, by dropping tethered corers from a ship to extract seafloor sediments that can be radiocarbon dated.”
Note: This story has been adapted from a news release issued by the University of Sheffield
Barrick Gold Corporation’s large open pit at its Goldstrike Mine on the Carlin Trend. The mine has Carlin-type gold deposits, the formation of which has been newly modeled by University of Nevada researchers. – Photo by John Mundean, University of Nevada, Reno and it’s public service department, the Nevada Bureau of Mines and Geology.
A team of University of Nevada, Reno and University of Nevada, Las Vegas researchers have devised a new model for how Nevada’s gold deposits formed, which may help in exploration efforts for new gold deposits.
The deposits, known as Carlin-type gold deposits, are characterized by extremely fine-grained nanometer-sized particles of gold adhered to pyrite over large areas that can extend to great depths. More gold has been mined from Carlin-type deposits in Nevada in the last 50 years – more than $200 billion worth at today’s gold prices – than was ever mined from during the California gold rush of the 1800s.
This current Nevada gold boom started in 1961 with the discovery of the Carlin gold mine, near the town of Carlin, at a spot where the early westward-moving prospectors missed the gold because it was too fine-grained to be readily seen. Since the 1960s, geologists have found clusters of these “Carlin-type” deposits throughout northern Nevada.
They constitute, after South Africa, the second largest concentration of gold on Earth. Despite their importance, geologists have argued for decades about how they formed.
“Carlin-type deposits are unique to Nevada in that they represent a perfect storm of Nevada’s ideal geology – a tectonic trigger and magmatic processes, resulting in extremely efficient transport and deposition of gold,” said John Muntean, a research economic geologist with the Nevada Bureau of Mines and Geology at the University of Nevada, Reno and previously an industry geologist who explored for gold in Nevada for many years.
“Understanding how these deposits formed is important because most of the deposits that cropped out at the surface have likely been found. Exploration is increasingly targeting deeper deposits. Such risky deep exploration requires expensive drilling.
“Our model for the formation of Carlin-type deposits may not directly result in new discoveries, but models for gold deposit formation play an important role in how companies explore by mitigating risk. Knowing how certain types of gold deposits form allows one to be more predictive by evaluating whether ore-forming processes operated in the right geologic
settings. This could lead to identification of potential new areas of discovery.”
Muntean collaborated with researchers from the University of Nevada, Las Vegas: Jean Cline, a facultyprofessor of geology at UNLV and a leading authority on Carlin-type gold deposits; Adam Simon, an assistant professor of geoscience who provided new experimental data and his expertise on the interplay between magmas and ore deposits; and Tony Longo, a post-doctoral fellow who carried out detailed microanalyses of the ore minerals.
The team combined decades of previous studies by research and industry geologists with new data of their own to reach their conclusions, which were written about in the Jan. 23 early online issue of Nature Geoscience magazine and will appear in the February printed edition. The team relates formation of the gold deposits to a change in plate tectonics and a major magma event about 40 million years ago. It is the most complete explanation for Carlin-type gold deposits to date.
“Our model won’t be the final word on Carlin-type deposits,” Muntean said. “We hope it spurs new research in Nevada, especially by people who may not necessarily be ore deposit geologists.”
Note: This story has been adapted from a news release issued by the University of Nevada, Reno
This is a schematic model of a river-coast system. – Geleynse et al
By adding information about the subsoil to an existing sedimentation and erosion model, researchers at Delft University of Technology (TU Delft, The Netherlands) have obtained a clearer picture of how rivers and deltas develop over time. A better understanding of the interaction between the subsoil and flow processes in a river-delta system can play a key role in civil engineering (delta management), but also in geology (especially in the work of reservoir geologists). Nathanaël Geleynse et al. recently published in the journals Geophysical Research Letters and Earth and Planetary Science Letters.
Model
Many factors are involved in how a river behaves and the creation of a river delta. Firstly, of course, there is the river itself. What kind of material does it transport to the delta? Does this material consist of small particles (clay) or larger particles (sand)? But other important factors include the extent of the tidal differences at the coast and the height of the waves whipped up by the wind. In this study, researchers at TU Delft are working together with Deltares and making use of the institute’s computer models (Delft3D software). These models already take a large number of variables into account. Geleynse et al. have now supplemented them with information on the subsoil. It transpires that this variable also exerts a significant influence on how the river behaves and the closely related process of delta formation.
Room for the River
The extra dimension that Geleynse et al. have added to the model is important to delta management, among other things. If – as the Delta Commission recommends – we should be creating “Room for the River”, it is important to know what a river will do with that space. Nathanaël Geleynse explains: “Existing data do not enable us to give ready-made answers to specific management questions … nature is not so easily tamed … but they do offer plausible explanations for the patterns and shapes we see on the surface. The flow system carries the signature of the subsoil, something we were relatively unaware of until now. Our model provides ample scope for further development and for studying various scenarios in the current structure.”
Geological information
River management is all about short-term and possible future scenarios. But the model developed by Geleynse et al. also offers greater insight into how a river/delta has developed over thousands of years. What might the subsoil have looked like and – a key factor for the oil industry – where might you expect to find oil reserves and what might their geometrical characteristics be? In combination with data from a limited number of core samples and other local measurements, the model can give a more detailed picture of the area in question than was possible until now.
The link between the creation of the delta and the structure of the delta subsoil is also of interest to engineers who wish to build there. Hundreds of millions of people across the globe live in deltas and these urban deltas are only expected to grow in the decades to come.
Note: This story has been adapted from a news release issued by the Delft University of Technology
Liu on the site of May 2008 Wenchuan earthquake in the Sichuan province of China, where more than 90,000 people died. Credit: Image courtesy of University of Missouri-Columbia
This December marks the bicentennial of the New Madrid earthquakes of 1811-12, which are the biggest earthquakes known to have occurred in the central U.S.
Now, based on the earthquake record in China, a University of Missouri researcher says that mid-continent earthquakes tend to move among fault systems, so the next big earthquake in the central U.S. may actually occur someplace else other than along the New Madrid faults.
Mian Liu, professor of geological sciences in the College of Arts and Science at MU, examined records from China, where earthquakes have been recorded and described for the past 2,000 years.
Surprisingly, he found that during this time period big earthquakes have never occurred twice in the same place.
“In North China, where large earthquakes occur relatively frequently, not a single one repeated on the same fault segment in the past two thousand years,” Liu said. “So we need to look at the ‘big picture’ of interacting faults, rather than focusing only on the faults where large earthquakes occurred in the recent past.”
Mid-continent earthquakes, such as the ones that occurred along the New Madrid faults, occur on a complicated system of interacting faults spread throughout a large region.
A large earthquake on one fault can increase the stress on other faults, making some of them more likely to have a major earthquake. The major faults may stay dormant for thousands of years and then wake up to have a short period of activity.
Along with co-authors Seth Stein, a professor of earth and planetary sciences at Northwestern University, and Hui Wang, a Chinese Earthquake Administration researcher, Liu believes this discovery will provide valuable information about the patterns of earthquakes in the central and eastern United States, northwestern Europe, and Australia. The results have been published in the journal Lithosphere.
“The New Madrid faults in the central U.S., for example, had three to four large events during 1811-12, and perhaps a few more in the past thousand years. This led scientists to believe that more were on the way,” Stein said. “However, high-precision Global Positioning System (GPS) measurements in the past two decades have found no significant strain in the New Madrid area.
The China results imply that the major earthquakes at New Madrid may be ending, as the pressure will eventually shift to another fault.”
While this study shows that mid-continent earthquakes seem to be more random than previously thought, the researchers believe it actually helps them better understand these seismic events.
“The rates of earthquake energy released on the major fault zones in North China are complementary,” Wang said. “Increasing seismic energy release on one fault zone was accompanied by decreasing energy on the others. This means that the fault zones are coupled mechanically.”
Studying fault coupling with GPS measurements, earthquake history, and computer simulation will allow the scientists to better understand the mysterious mid-continent earthquakes.
“What we’ve discovered about mid-continent earthquakes won’t make forecasting them any easier, but it should help,” Liu said.
Note: This story has been adapted from a news release issued by the University of Missouri-Columbia
