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Presto, Change-o!

Extraterrestrial impacts transform Earth's surface in an instant

By
7:33pm, June 11, 2002

Most geological processes unfold at less than a snail's pace. The tectonic plates that cover Earth's surface slog along, crashing into and sliding over one another at rates of only a few millimeters per year. Over millions of years, however, these unhurried liaisons raise mountain ranges. Wind, rain, and natural chemical erosion gradually rework the mountains into silt, clay, and dissolved minerals. Slowly, this inorganic detritus wends its way to the sea, where it joins a languid rain of dead marine organisms to form thick layers of ocean-floor ooze.

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