When continents formed
2011-01-14
(Press-News.org) The continental crust is the principal record of conditions on the Earth for the last 4.4 billion years. Its formation modified the composition of the mantle and the atmosphere, it supports life, and it remains a sink for carbon dioxide through weathering and erosion. The continental crust therefore has had a key role in the evolution of the Earth, and yet the timing of its generation remains the topic of considerable debate.
It is widely believed that the juvenile continental crust has grown from the depleted upper mantle. One common way to assess when new crust was formed is to determine the radiogenic isotope composition of any crustal sample, and to compare its isotope signature with that of the depleted mantle. In other words, radiogenic isotopes can be used to calculate 'model ages' of crust formation, which represent the time since a crustal sample was separated from its mantle source.
The concept of 'model age' has been widely used in crustal evolution studies for the last three decades. However it is increasingly clear that using the isotope composition of the depleted mantle as a reference for the calculation of model ages of continental crust generation can lead to incomplete interpretations.
In a paper published today in Science, Dr Bruno Dhuime of Bristol's School of Earth Sciences and colleagues describe a new methodology for the calculation of model ages, based on the isotope composition of the average new continental crust.
Dr Dhuime said: "Ages calculated this way are significantly younger than model ages calculated from the isotope composition of the depleted mantle. New ages obtained are more consistent with the geological record, which opens new perspectives in crustal evolution studies based on radiogenic isotopes."
###
END
ELSE PRESS RELEASES FROM THIS DATE:
2011-01-14
CHAMPAIGN, Ill. — Researchers report that they can predict "with unprecedented accuracy" how well you will do on a complex task such as a strategic video game simply by analyzing activity in a specific region of your brain.
The findings, published in the online journal PLoS ONE, offer detailed insights into the brain structures that facilitate learning, and may lead to the development of training strategies tailored to individual strengths and weaknesses.
The new approach used established brain imaging techniques in a new way. Instead of measuring how brain activity ...
2011-01-14
Airborne prions are also infectious and can induce mad cow disease or Creutzfeldt-Jakob disorder. This is the surprising conclusion of researchers at the University of Zurich, the University Hospital Zurich and the University of Tübingen. They recommend precautionary measures for scientific labs, slaughterhouses and animal feed plants.
The prion is the infectious agent that caused the epidemic of mad cow disease, also termed bovine spongiform encephalopathy (BSE), and claimed the life of over 280,000 cows in the past decades. Transmission of BSE to humans, e.g. by ...
2011-01-14
A team of paleontologists and geologists from Argentina and the United States on Jan. 13 announced the discovery of a lanky dinosaur that roamed South America in search of prey as the age of dinosaurs began, approximately 230 million years ago.
Sporting a long neck and tail and weighing only 10 to 15 pounds, the new dinosaur has been named Eodromaeus, the "dawn runner."
"It really is the earliest look we have at the long line of meat eaters that would ultimately culminate in Tyrannosaurus rex near the end of the dinosaur era," said Paul Sereno, University of Chicago ...
2011-01-14
Irvine, Calif. — The reward systems at universities heavily favor science, math and engineering research at the expense of teaching, which can and must change. That's the conclusion of UC Irvine biology professor Diane K. O'Dowd and research professors at Harvard University, Yale University, the Massachusetts Institute of Technology, and elsewhere.
Writing in the Jan. 14 issue of Science magazine, the authors note that professors have two responsibilities: to generate new knowledge and to educate students. But, they maintain, "although education and lifelong learning ...
2011-01-14
Researchers from Cardiff University are opening up a new way of using hydrocarbon feedstocks to make a range of valuable products.
Hydrocarbons are an extremely important energy resource but, although widely available from fossil fuels, are extremely difficult to activate and require very high temperatures in current industrial processes.
For the first time, the Cardiff study has shown that the primary carbon-hydrogen bonds in toluene, a hydrocarbon widely used as an industrial material, can be activated selectively at low temperatures.
Professor Graham Hutchings ...
2011-01-14
ANN ARBOR, Mich. – Surviving cancer may also mean surviving pain, according to a study by the University of Michigan Health System showing 20 percent of cancer survivors at least two years post diagnosis have current cancer-related chronic pain.
The study, published online ahead of print in the American Cancer Society's journal Cancer, gives new insight on issues in cancer survivorship among the growing number of U.S. cancer survivors.
More than 40 percent of patients surveyed had experienced pain since their diagnosis, and the pain experience was worse for blacks ...
2011-01-14
Adults who take one of the world's most commonly prescribed sleep medications are significantly more at risk for nighttime falls and potential injury, according to a new study by the University of Colorado at Boulder.
The study, which involved 25 healthy adults, showed 58 percent of the older adults and 27 percent of the young adults who took a hypnotic, sleep-inducing drug called zolpidem showed a significant loss of balance when awakened two hours after sleep. The findings are important because falls are the leading cause of injury in older adults, and 30 percent of ...
2011-01-14
(Santa Barbara, Calif.) –– Planck –– an international satellite that peers back into the beginning of the universe –– has produced what scientists are calling new and provocative data. The satellite is a European Space Agency mission with significant contributions from NASA.
On Tuesday, the Planck mission released a new data catalog with initial maps of the entire sky. The catalog includes thousands of never-before-seen dusty cocoons where stars are forming, and some of the most massive clusters of galaxies ever observed.
"Encoded in the Planck maps is an enormous ...
2011-01-14
Doctors are calling for women to receive more information about the pitfalls of breast cancer screening, as well as the benefits, after some women who received false-positive results faced serious anxiety and reduced quality of life for at least a year.
A study published online by BJS, the British Journal of Surgery, shows that patients with false-positive results - where the mammogram is abnormal but no cancer is present - had to undergo more diagnostic procedures than women with breast cancer before they were given the all clear.
Researchers from The Netherlands ...
2011-01-14
The first gravitational lens, a phenomenon in which light from a distant object is bent around a massive foreground object, was discovered in 1979 by a team led by Dr. Dennis Walsh from The University of Manchester's Jodrell Bank Observatory.
Since then, astronomers have used gravitational lenses in many ways, including studying dark matter and as "Nature's Telescope" to investigate galaxies in the distant universe.
In a letter to the journal Nature, Professor Shude Mao of The University of Manchester, along with Stuart Wyithe (University of Melbourne), Haojing Yan ...
LAST 30 PRESS RELEASES:
[Press-News.org] When continents formed
