Midwestern Earthquakes? --Blame Old Glaciers.(Brief Article)(Statistical Data Included)

Publication: USA Today (Magazine)

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COPYRIGHT 2001 Society for the Advancement of Education

The ghost of past glaciers may still rattle the American Midwest, Until 20,000 years ago, a gigantic ice sheet covered North America, weighing down the hard upper crust of the continent for millions of years. Eventually, the glaciers melted. Freed from the heavy pressure of the ice sheet, North America slowly rose. This glacial rebound continues today and triggers quakes in the New Madrid fault zone in Missouri, Kentucky, Arkansas, and Tennessee, according to Stanford (Calif.) University geophysicist Mark Zoback. "It's the only hypothesis we have that I think satisfies all the diverse observations, especially that big earthquakes in this region appear to have been turned on during the past few thousands of years."

His theory explains earthquakes that occur in the middle of the North American continent,...

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