The town of New Madrid lies directly on a fault line that runs along the Mississippi River. It formed when Africa and North America split up two hundred million years ago.

During an earthquake, violent tremors cause layers of wet sand underground to shake. Under strong pressure this muddy sand works its way upward through the cracks in the earth’s crust, gushing out as a sand blow or sand volcano. The remnants of these can be seen from the air as light patches on the ground.

Martitia Tuttle is studying these sand blows to predict when the next big one will be. Until very recently geologists thought earthquakes near New Madrid happened once every two thousand years.

By painstakingly dating the organic material in these sand blows, Tuttle has discovered that earthquakes here are a lot more frequent – occurring every five hundred years.


  • In 1812, the largest earthquake ever recorded in the United States (magnitude 8) shook the entire east coast, large areas of land sank into the earth, and new lakes formed. Nearby sections of the Mississippi River ran backwards for a time changing the course of the river.

  • The Great Lakes
    Discover the roots of a long vanished mountain range, explore the remains of an inland tropical sea and trace the story of a dramatic flood
  • The Rockies
    An ever-changing landmass, geologists are learning how the Rockies were formed and discovering what they will become.
  • The Canadian Shield
    The largest - and one of the oldest - expanses of ancient rock on the planet has riches of gold and diamonds under it's crust.
  • The Appalachians
    These fabled mountains contain a geologic puzzle, a rich legacy, and the scarcely known threat of earthquakes.
  • The Atlantic Coast
    The dramatic story of volcanic outpourings, massive rifting of continents and the bursting forth of a new ocean - the Atlantic.

A five-part series that chronicles the incredible—and surprising—history of Canada's landscape in HD.

Canada Rocks Read an excerpt from Canada Rocks, a new book by the scientific advisor to Geologic Journey, Nick Eyles.

Watch video interviews with some of the scientists featured in Geologic Journey (produced in conjunction with National Sciences and Engineering Research Council of Canada).

Order the Geologic Journey DVD for classroom use and download Teacher Resource Materials.
The Nature of Things with David Suzuki
Fault Line: A rock fracture, which shows evidence of movement. Large faults within the Earth's crust are the result of shear motion and active fault zones are the cause of most earthquakes.