When a massive and mysterious hole was discovered in Siberia last July (see pictures), social media users pointed to everything from a meteorite to a stray missile to aliens to the Bermuda Triangle as possible causes. But the most plausible explanation seemed to be the explosive release of melting methane hydrate—an ice-like material frozen in the Arctic ground—thanks to global warming.
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Now, scientists are arguing that the methane theory is unlikely, based on new satellite surveys released by Russian researchers that found dozens of new craters in Siberia.
“The jury is still out” on the cause of Siberia’s craters, says Carolyn Ruppel, chief of the U.S. Geological Survey’s Gas Hydrates Project. But she and other scientists say the new satellite mapping suggests another explanation that has to do with the rapid melting of ice cores called pingos.
A pingo is a plug of ice that forms near the surface over time and has a small mound or hill on top.
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