June 1, 2006, 6:34 PM CT

Killer Crater Found Under Ice

Planetary researchers have found evidence of a meteor impact much larger and earlier than the one that killed the dinosaurs -- an impact that they believe caused the biggest mass extinction in Earth's history.

The 300-mile-wide crater lies hidden more than a mile beneath the East Antarctic Ice Sheet. And the gravity measurements that reveal its existence suggest that it could date back about 250 million years -- the time of the Permian-Triassic extinction, when almost all animal life on Earth died out.

Its size and location -- in the Wilkes Land region of East Antarctica, south of Australia -- also suggest that it could have begun the breakup of the Gondwana supercontinent by creating the tectonic rift that pushed Australia northward.

Researchers think that the Permian-Triassic extinction paved the way for the dinosaurs to rise to prominence. The Wilkes Land crater is more than twice the size of the Chicxulub crater in the Yucatan peninsula, which marks the impact that may have ultimately killed the dinosaurs 65 million years ago. The Chicxulub meteor is thought to have been 6 miles wide, while the Wilkes Land meteor could have been up to 30 miles wide -- four or five times wider.

"This Wilkes Land impact is much bigger than the impact that killed the dinosaurs, and probably would have caused catastrophic damage at the time," said Ralph von Frese, a professor of geological sciences at Ohio State University.........

Posted by: William      Permalink         Source

May 31, 2006, 9:19 PM CT

Climate History Rewritten

For the first time, researchers have pulled up prehistoric geologic records from the frigid vault of the Arctic Ocean. One of the findings, evidence of glacial Arctic ice from 45 million years ago, recasts a critical chapter of global climate history.

The evidence - pea-sized pebbles locked inside a 430 meter-long sediment core - shows that glaciers formed in the Arctic Ocean about 14 million years earlier than geologists had thought. This means that the immense sheets of ice at the Earth's poles formed simultaneously, something scientists call "bipolar symmetry" in one of three reports on Arctic ice highlighted on the cover of Nature.

Previously, geologists believed glaciers formed in Antarctica long before they appeared in the Arctic. The new evidence clears up this climate mystery and underscores the role that carbon dioxide and other greenhouse gases play in climate change, as per Steven Clemens, associate professor (research) in the Department of Geological Sciences at Brown University and a co-author of the Nature papers.

"In the past, researchers thought shifting tectonic plates and changes in ocean circulation patterns in the Southern Hemisphere may have prompted ice to form earlier in Antarctica," Clemens said. "But there was other data that contradicted this theory. Now much of what we know about the evolution of ice on Earth makes more sense. And the evidence underscores the importance of greenhouse gases as a driver of climate change. If you inject or remove large amounts of carbon in the atmosphere, you get truly global climate change".........

Posted by: Tyler      Permalink         Source

May 30, 2006, 11:14 PM CT

Climate Change Responsible For Increased Hurricanes

Human induced climate change, rather than naturally occurring ocean cycles, may be responsible for the recent increases in frequency and strength of North Atlantic hurricanes, as per Penn State and Massachusetts Institute of Technology researchers.

"Anthropogenic factors are likely responsible for long-term trends in tropical Atlantic warmth and tropical cyclone activity," the scientists report in an upcoming issue of the American Geophysical Society's EOS.

Michael E. Mann, associate professor of meteorology and geosciences, Penn State, and Kerry A. Emanuel, professor of atmospheric sciences, MIT, looked at the record of global sea surface temperatures, hurricane frequency, aerosol impacts and the so-called Atlantic Multidecadal Oscillation (AMO) Ð an ocean cycle similar, but weaker and less frequent than the El Nino/La Nina cycle. Eventhough others have suggested that the AMO, a cycle of from 50 to 70 years, is the significant contributing factor to the increase in number and strength of hurricanes, their statistical analysis and modeling indicate that it is only the tropical Atlantic sea surface temperature that is responsible, tempered by the cooling effects of some lower atmospheric pollutants.

"We only have a good record of hurricanes and sea surface temperature for a little more than the last 100 years," says Mann, who is also director of Penn State's Earth System Science Center. "This means we have only observed about one and a half to two cycles of the AMO. Peer-reviewed research does suggest that the signal exists, but it is difficult to estimate the period and magnitude of the oscillation directly from observations."........

Posted by: Tyler      Permalink         Source

May 26, 2006, 0:04 AM CT

Eruption At Undersea Volcano

An international team of researchers has presented its findings from the first observations of the eruption of a submarine volcano that in 2004 and 2005 spewed out plumes of sulfur-rich fluid and pulses of volcanic ash 550 meters below the ocean's surface near the Mariana Islands northwest of Guam.

Those findings will be published Thursday in Nature - just after a number of of those same researchers returned from another expedition to the site, where they observed new bursts of erupting lava.

The scientists have now observed eruptive activity at the site during three separate visits over a period of more than two years, suggesting that these types of deep-sea volcanoes erupt chronically for longer periods than other undersea volcanoes located on the mid-ocean ridge. The eruptive activity they just observed at a volcano dubbed Northwest Rota-1 was explosive, but provided some of the closest observations ever of a volcano, thanks to the help of an underwater robot.

"We were forced to evacuate the remotely operated vehicle, 'Jason II,' several times to avoid getting it enveloped in volcanic clouds," said Bill Chadwick, an Oregon State University volcanologist and one of the authors of the study. "But at other times, we could observe the eruption from only 10 feet away - something you could never do on land. So in some ways, we were able to see processes more clearly at the bottom of the ocean than we ever could on land. That was surprising."........

Posted by: Tyler      Permalink         Source

May 25, 2006, 10:45 PM CT

Colorado River Streamflows Reconstructed

A new tree-ring-based reconstruction of 508 years of Colorado River streamflow confirms that droughts more severe than the 2000-2004 drought occurred before stream gages were installed on the river.

The new research also confirms that using stream gage records alone may overestimate the average amount of water in the river because the last 100-year period was wetter than the average for the last five centuries.

"This work updates the original landmark Colorado River reconstruction that was done at The University of Arizona's Laboratory of Tree-Ring Research," said David M. Meko, a UA associate research professor of dendrochronology, the science of tree-ring dating.

"The main points of the 1976 research hold up. Droughts more severe and intense than we've seen in the gaged record occurred in the past, and the long-term mean flow is lower than the gaged mean flow."

Connie A. Woodhouse said, "The updated reconstruction for Lee's Ferry indicates that as a number of as eight droughts similar in severity, in terms of average flow, to the 5-year 2000-2004 drought have occurred since 1500."

Woodhouse, who led the research team, is a physical scientist at the National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center Paleoclimatogy Branch in Boulder, Colo.........

Posted by: Tyler      Permalink         Source

May 24, 2006, 0:10 AM CT

Tibet Pathway For Chemicals

Scientists from Georgia Tech and NASA have found that thunderstorms over Tibet provide a main pathway for water vapor and chemicals to travel from the lower atmosphere, where human activity directly affects atmospheric composition, into the stratosphere, where the protective ozone layer resides.

Learning how water vapor reaches the stratosphere can help improve climate prediction models. Similarly, understanding the pathways that ozone-depleting chemicals can take to reach the stratosphere is essential for understanding future threats to the ozone layer, which shields Earth from the sun's harmful ultraviolet rays.

Scientists from the Georgia Institute of Technology, Atlanta; NASA's Jet Propulsion Laboratory, Pasadena, Calif.; and the University of Edinburgh, Scotland, performed their analysis using data from the Microwave Limb Sounder instrument on NASA's Aura spacecraft, combined with data from NASA's Aqua and Tropical Rainfall Measuring Missions.

The team collected more than 1,000 measurements of high concentrations of water vapor in the stratosphere over the Tibetan Plateau and the Asian monsoon region. The measurements were collected during August 2004 and August 2005, during the height of monsoon season. Through the use of wind data and NASA atmospheric models, they found the water vapor originated over Tibet, just north of the Himalayan mountain range.........

Posted by: Sarah      Permalink         Source

May 23, 2006, 11:51 PM CT

US Ports Vulnerable To Devastating Earthquake Damage

If a repeat of the 1906 San Francisco earthquake were to occur, and the Port of Oakland were so severely damaged that it took as long as two years to resume full operations, what would be the impact on the U.S. economy?.

U.S. ports serve as crucial gateways for international trade, but they're especially vulnerable to damage in an earthquake. Western U.S. ports in Oakland, Los Angeles, Long Beach and Seattle are at the greatest risk for earthquake damage, but eastern U.S. ports in Charleston, S.C., and Savannah, Ga., are also at risk.

A new project led by the Georgia Institute of Technology aims to develop strategies to help safeguard ports from earthquake damage. The project, sponsored by the National Science Foundation (NSF), has $3.6 million in funding over the next five years.

"Ports are a critical civil infrastructure system," said Glenn J. Rix, a professor in Georgia Tech's School of Civil and Environmental Engineering and the project director. "Given the growth in international trade, we don't think seismic risks at ports have received the proper amount of attention. If a large portion of a major U.S. port such as Oakland or Los Angeles were out of service for a year because of an earthquake, there would be significant economic consequences for the United States."........

Posted by: Tom      Permalink         Source

May 21, 2006, 9:45 AM CT

Cluster Flies Through Earth's Electrical Switch

ESA's Cluster satellites have flown through regions of the Earth's magnetic field that accelerate electrons to approximately one hundredth the speed of light. The observations present Cluster researchers with their first detection of these events and give them a look at the details of a universal process known as magnetic reconnection.

On 25 January 2005, the four Cluster spacecraft found themselves in the right place at the right time: a region of space known as an electron diffusion region. It is a boundary just a few kilometres thick that occurs at an altitude of approximately 60 000 kilometres above the Earth's surface. It marks the frontier between the Earth's magnetic field and that of the Sun. The Sun's magnetic field is carried to the Earth by a wind of electrically charged particles, known as the solar wind.

An electron diffusion region is like an electrical switch. When it is flipped, it uses energy stored in the Sun's and Earth's magnetic fields to heat the electrically charged particles in its vicinity to large speeds. In this way, it initiates a process that can result in the creation of the aurora on Earth, where fast-moving charged particles collide with atmospheric atoms and make them glow.

There is also a more sinister side to the electron diffusion regions. The accelerated particles can damage satellites by colliding with them and causing electrical charges to build up. These short circuit and destroy sensitive equipment.........

Posted by: Brooke      Permalink         Source

May 18, 2006, 11:00 PM CT

Linking Climate Change Across Time Scales

What do month-to-month changes in temperature have to do with century-to-century changes in temperature? At first it might seem like not much. But in a report published in this week's Nature, researchers from the Woods Hole Oceanographic Institution (WHOI) have found some unifying themes in the global variations of temperature at time scales ranging from a single season to hundreds of thousands of years. These findings help place climate observed at individual places and times into a larger global and temporal context.

"Much of the work went into assembling the different types of records needed to study such diverse time scales", said Peter Huybers, a paleoclimatologist in the Geology and Geophysics Department at WHOI and lead author on the study. "Data from instruments from around the world are available for recent periods, but it is not so easy for earlier times. We have few instrumental records before the 19th century, so we have to use measurements in corals, ice cores, and sediment cores to estimate past temperatures".

These measurements and data compilations were made by researchers at WHOI and other research institutions. "While none of the measurements we use are new," Huybers said, "putting them together told us more than we could learn from any single record".........

Posted by: William      Permalink         Source

May 18, 2006, 9:33 PM CT

Aorounga Impact Crater, Chad

The impact of an asteroid or comet several hundred million years ago left scars in the landscape that are still visible in this spaceborne radar image of an area in the Sahara Desert of northern Chad. The concentric ring structure is the Aorounga impact crater, with a diameter of about 17 kilometers (10.5 miles). The original crater was buried by sediments, which were then partially eroded to reveal the current ring-like appearance. The dark streaks are deposits of windblown sand that migrate along valleys cut by thousands of years of wind erosion.

The dark band in the upper right of the image is a portion of a proposed second crater. Researchers are using radar images to investigate the possibility that Aorounga is one of a string of impact craters formed by multiple impacts. Radar imaging is a valuable tool for the study of desert regions because the radar waves can penetrate thin layers of dry sand to reveal details of geologic structure that are invisible to other sensors. The image was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) on April 18 and 19, 1994, onboard the space shuttle Endeavour. The area shown is 22 kilometers by 28 kilometers (14 miles by 17 miles) and is centered at 19.1 degrees north latitude, 19.3 degrees east longitude. North is toward the upper right. The colors are assigned to different radar frequencies and polarizations as follows: red is L-band, horizontally transmitted and received; green is C-band, horizontally transmitted and received; and blue is C-band, horizontally transmitted, vertically received. SIR-C/X-SAR, a joint mission of the German, Italian and United States space agencies, is part of NASA's Mission to Planet Earth program.........

Posted by: Brooke      Permalink         Source

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