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6 March 2014 1:04 pm ,
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Magdalena Koziol, a former postdoc at Yale University, was the victim of scientific sabotage. Now, she is suing the...
Antiretroviral drugs can protect people from becoming infected by HIV. But so-called pre-exposure prophylaxis, or PrEP...
Two studies show that eating a diet low in protein and high in carbohydrates is linked to a longer, healthier life, and...
Considered an icon of conservation science, researchers at World Wildlife Fund (WWF) headquarters in Washington, D.C.,...
The new atlas, which shows the distribution of important trace metals and other substances, is the first product of...
Early in April, the first of a fleet of environmental monitoring satellites will lift off from Europe's spaceport in...
Since 2000, U.S. government health research agencies have spent almost $1 billion on an effort to churn out thousands...
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ScienceShot: Erosion in Flatland
1 February 2013 12:05 pm
Who says Earth's not flat? Even though more than half of the planet's ice-free terrain has a slope of 0.6° or less, where water flow is generally languid, a significant part of the world's erosion takes place there, a new study reveals. By analyzing river sediments collected at thousands of locations worldwide and estimating their concentration of the isotope beryllium-10 (which is produced when cosmic rays strike rocks at or near Earth's surface), researchers could assess rates of erosion in those watersheds. For watersheds with areas ranging between 1 and 10,000 square kilometers, rates of erosion were strongly correlated with the average steepness of the watershed when that slope exceeded 11.3° (a rise of 200 meters for every horizontal kilometer). Rates of erosion were less predictable in more gently sloping landscapes, but data suggest that the breakdown of rocks in ice-free terrain creates about 5.5 billion tons of sediment worldwide each year, the researchers report in a forthcoming issue of Geology. Although erosion can remove as much as 6 meters of material in mountainous areas (such as in the Grand Tetons in the above background) each millennium, in gently sloping areas (foreground) wind and water may strip away as little as 0.5 millimeters per year. Overall, at least half Earth's surface loses about 12 millimeters or more to erosion every 1000 years, the team estimates. Altogether, about 80% of the world's sediment is produced by erosion of terrain with a slope of 6° or less.
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