Deep below the Deepwater Horizon oil spill
Researchers discover new force driving Earth’s tectonic plates
Using analytical methods to track plate motions through Earth’s history, Cande and Stegman’s research provides evidence that such mantle plume “hot spots,” which can last for tens of millions of years and are active today at locations such as Hawaii, Iceland and the Galapagos, may work as an additional tectonic driver, along with push-pull forces.
The team also recognized that this “plume-push” force acted on other tectonic plates, and pushed on Africa as well but in the opposite direction.
After the force of the plume had waned, the African plate’s motion gradually returned to its previous speed while India slowed down.
Ocean currents speed melting of Antarctic ice
“More warm water from the deep ocean is entering the cavity beneath the ice shelf, and it is warmest where the ice is thickest,” said study’s lead author, Stan Jacobs, an oceanographer at Columbia University’s Lamont-Doherty Earth Observatory.
In 2009, Jacobs and an international team of scientists sailed to the Amundsen Sea aboard the icebreaking ship Nathaniel B. Palmer to study the region’s thinning ice shelves-floating tongues of ice where landbound glaciers meet the sea. One goal was to study oceanic changes near the Pine Island Glacier Ice Shelf, which they had visited in an earlier expedition, in 1994. The researchers found that in 15 years, melting beneath the ice shelf had risen by about 50 percent. Although regional ocean temperatures had also warmed slightly, by 0.2 degrees C or so, that was not enough to account for the jump.
One day, near the southern edge of Pine Island Glacier Ice Shelf, the researchers directly observed the strength of the melting process as they watched frigid, seawater appear to boil on the surface like a kettle on the stove. To Jacobs, it suggested that deep water, buoyed by added fresh glacial melt, was rising to the surface in a process called upwelling. Jacobs had never witnessed upwelling first hand, but colleagues had described something similar in the fjords of Greenland, where summer runoff and melting glacier fronts can also drive buoyant plumes to the sea surface.
Pine Island Glacier, among other ice streams in Antarctica, is being closely watched for its potential to redraw coastlines worldwide. Global sea levels are currently rising at about 3 millimeters (.12 inches) a year. By one estimate, the total collapse of Pine Island Glacier and its tributaries could raise sea level by 24 centimeters (9 inches).
Stiff sediments made 2004 Sumatra earthquake deadliest in history
Instead of the usual weak, loose sediments typically found above the type of geologic fault that caused the earthquake, the team found a thick plateau of hard, compacted sediments. Once the fault snapped, the rupture was able to spread from tens of kilometers below the seafloor to just a few kilometers below the seafloor, much farther than weak sediments would have permitted. The extra distance allowed it to move a larger column of seawater above it, unleashing much larger tsunami waves.
“The results suggest we should be concerned about locations with large thicknesses of sediments in the trench, especially those which have built marginal plateaus,” said Sean Gulick, research scientist at The University of Texas at Austin’s Institute for Geophysics. “These may promote more seaward rupture during great earthquakes and a more significant tsunami.”
The team’s results appear this week in an article lead-authored by Gulick in an advance online publication of the journal Nature Geoscience.
The team from The University of Texas at Austin, The University of Southampton in the United Kingdom, The Agency for the Assessment and Application of Technology in Indonesia and The Indonesia Institute for Sciences used seismic instruments, which emit sound waves, to visualize subsurface structures.
The earthquake struck along a fault where the Indo-Australian plate is being pushed beneath the Sunda plate to the east. This is known as a subduction zone and in this case the plates meet at the Sunda Trench, around 300km west of Sumatra. The Indo-Australian plate normally moves slowly under the Sunda plate, but when the rupture occurred, it violently surged forward.
Subduction earthquakes are thought to start tens of kilometers beneath the Earth’s surface. Displacement or “slip” on the fault, as geologists call it, propagates upwards and generally dissipates as it reaches weaker rocks closer to the surface. If it were an ordinary seismic zone, the sediment in the Sunda Trench should have slowed the upward and westward journey of the 2004 earthquake, generating a tsunami in the shallower water on the landward (east) side of the trench.
But in fact the fault slip seems to have reached close to the trench, lifting large sections of the seabed in deeper water and producing a much larger tsunami.
Earth from space: A gush of volcanic gas
Going with the flow: Researchers find compaction bands in sandstone are permeable
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.
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.
Team debunks theory on end of ‘Snowball Earth’ ice age
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.
Unusual earthquake gave Japan tsunami extra punch, say Stanford scientists
‘Fool’s Gold’ from the deep is fertilizer for ocean life
Because the nanoparticles are so small, they are dispersed into the ocean rather than falling to the sea floor.
Geologist leads team effort to solve mystery of the Colorado Plateau
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.
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.
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.”
Melting ice on Arctic islands a major player in sea level rise
“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.
Future tsunamis and storm surges, for example, would more easily overtop ocean barriers.
Electric Yellowstone
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 Yellowstone Hotspot at a Glance
Computing a Geoelectrical Image of Yellowstone’s Hotspot Plume
Newly discovered natural arch in Afghanistan one of world’s largest
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.
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.”
Deep-sea volcanoes don’t just produce lava flows, they also explode!
But no one has been able to prove it until now.
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.
Researchers help map tsunami and earthquake damage in Japan
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.
They are mapping the area around the power plant as well, processing imagery from a broader view of the terrain used as farmland.
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.
Ancient ‘hyperthermals’ a guide to anticipated climate changes
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.
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.
Viscous cycle: Quartz is key to plate tectonics
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.
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.
The scientists describe a new approach to measuring properties of the deep crust.
68 percent of New England and Mid-Atlantic beaches eroding
Scientists delve into ‘hotspot’ volcanoes along Pacific Ocean Seamount Trail
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.
“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.
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.
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 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.
“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.
“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.