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6 March 2014 1:04 pm ,
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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...
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...
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ScienceShot: Underground Rain Gauge?
12 June 2012 5:25 pm
Cave formations known as stalactites are often pretty, but they also may provide clues about past climates. In some instances, the surfaces of these icicle-like accumulations of minerals sport series of rings, ripples, and ridges (image) which are typically spaced between 5 and 10 millimeters apart. A new analysis suggests that the ridges develop when the steady flow of mineral-rich water is disturbed as it runs over tiny imperfections in a stalactite's surface. Small eddies in the flow lead to increased deposition of calcium carbonate at certain regularly spaced locations, researchers reported online this month in Physical Review Letters. Cross sections through stalactites reveal that even though water is flowing downward, these regular ridges, or crenulations, migrate upward as years pass because deposition of minerals tends to take place on the upstream side of the ridges. According to the team's model, the rate at which the crenulations migrate upward doesn't depend on the temperature in the cave or the concentration of dissolved minerals in the water. However, the migration rate does depend on the flow rate of the water across a stalactite's surface—a hint that scientists might be able to use crenulated stalactites as rain gauges for past eras, since the amount of water dripping down a stalactite's surface typically depends on the precipitation falling on the surface above the cave.
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