Academic journal article The Science Teacher

Ancient Glaciers

Academic journal article The Science Teacher

Ancient Glaciers

Article excerpt

Long after the disappearance of the glaciers that once covered much of North America, the land they rested on is still recovering from their weight--and the slow movement of this recovery includes horizontal motion never seen before, say Purdue scientists.

The research team, led by Eric A. Calais, an associate professor of geophysics in Purdue's College of Science, has found that a large swath of territory in the Northeast is slowly moving southward in relation to the rest of the continent. This region, once covered with massive ice sheets heavy enough to deform the very stone they rested on, has long been known to be rising slowly in response to the glaciers' retreat, but this response has now been observed to have a horizontal component as well.

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"We already knew that parts of North America are slowly rising due to an effect we call post-glacial rebound," Calais says. "The weight of the ice sheets that once covered the region was large enough to deflect the surface beneath it, lowering its elevation. Now that the ice sheets are gone, the land is recovering slowly--so slowly that it is still rising today, 10,000 years later." What the team's study showed, however, was that the region is not merely rising in elevation, but also expanding outward at a slow but noticeable rate. …

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