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5 December 2013 11:26 am ,
Vol. 342 ,
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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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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