Since we can't sample the deepest regions of the Earth, scientists watch the velocity of seismic waves as they travel through the planet to determine the composition and density of that material. Now a new study suggests that material in part of the lower mantle has unusual electronic characteristics that make sound propagate more slowly, suggesting that the material there is softer than previously thought. The results call into question the traditional techniques for understanding this region of the planet. The authors, including Alexander Goncharov from the Carnegie Institution's Geophysical Laboratory, present their results in the January 25, 2008, issue of Science.
The lower mantle extends from about 400 miles to 1800 miles (660-2900 kilometers) into Earth and sits atop the outer core. Pressures and temperatures are so brutal there that materials are changed into forms that don't exist in rocks at the planet's surface and must be studied under carefully controlled conditions in the laboratory. The pressures range from 230,000 times the atmospheric pressure at sea level (23 GPa), to 1.35 million times sea-level pressure (135 GPa). And the heat is equally extreme - from about 2,800 to 6,700 degrees Fahrenheit (1800K - 4000K).
Rebecca Morelle
BBCThu, 24 Jan 2008 14:46 UTC
Scientists believe they could be a step closer to solving the mystery of how the first birds took to the air.
A study published in the journal
Nature suggests that the key to understanding the evolution of bird flight is the angle at which a bird flaps its wings.
The US team found that birds move their wings at the same narrow angle, whether they run, fly or glide.
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AFP Wed, 23 Jan 2008 17:14 UTC
JAKARTA - A strong 6.2-magnitude quake rattled the remote Indonesian island of Nias, off the west coast of Sumatra, early Wednesday, leaving one person dead and four injured, the police said.
BEIJING -- An earthquake measuring 5.5 degrees on Richter Scale hit Tibet at 2:43 Beijing Time Wednesday, according to the China Seismological Monitoring Network.
SANTIAGO -- A 5.2-magnitude earthquake hit the First Region in northern Chile Tuesday morning, according to a Seismic Monitoring Network of the University of Chile
The Arctic ice cap has shrunk by an area twice the size of France's land mass over the last two years, the Paris-based National Centre for Scientific Research (CNRS) said Wednesday.
Lake Norman, North Carolina - Nuclear reactors across the Southeast could be forced to throttle back or temporarily shut down later this year because drought is drying up the rivers and lakes that supply power plants with the awesome amounts of cooling water they need to operate.
In Cooch Behar district, the district's animal resources department sources said deaths of chicken were reported at Khalisamari of Mathabhanga-I block. ARD sources in the district said that bird deaths were reported from four blocks out of 12. These were Dinhata-I, Cooch Behar-I, Mathabhanga-I and Mekhliganj. In Haribhanga of Cooch Behar-I, carcasses of 10 migratory birds were found yesterday. The samples were sent to Kolkata.
Temperatures on Earth have stabilized in the past decade, and the planet should brace itself for a new Ice Age rather than global warming, a Russian scientist said in an interview with RIA Novosti Tuesday.
Global conservation group WWF called on Tuesday for a moratorium on all new oil exploration in the Arctic, insisting that the environmental risks to the sensitive eco system there were too great.
"The WWF is formally calling for a moratorium on new oil and gas development in the Arctic," Neil Hamilton, director of the group's Arctic programme, said at a conference in northern Norway on environmental challenges in the polar region.
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