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The continents are constantly moving, although the motion is far too slow for humans to notice. Earth's surface is divided into massive tectonic plates that drift at about the same speed as your fingernails grow. Over millions of years, these movements create mountains, trigger earthquakes, and reshape oceans. Scientists believe all the continents were once joined together in a supercontinent called Pangaea. The study of plate tectonics has transformed our understanding of Earth's history.
© United States Geological Survey
