A supercontinent that stayed put

Sandstone in Vermillion Cliffs National Monument, Arizona composed of the deposits of one very large, Jurassic sand dune.

For about 100 million years of Earth’s history, from the Permian through the Jurassic periods,, all of Earth’s continents were actually joined as a single supercontinent, called Pangea (“pan-JEE-uh”). It began breaking up during the Jurassic, forming the continents Gondwanaland and Laurasia.

Sandstone cliff in Vermillion Cliffs National Monument, Arizona composed of the deposits of three large, Jurassic sand dunes (person for scale in lower center).

Scientists have generally thought that Pangea, which was originally centered roughly on the equator, drifted northward to about 20 degrees latitude, roughly where the southern United States is today.

A new study by Clinton M. Rowe of the University of Nebraska and his colleagues now suggests that Pangea may have stayed put at the equator instead.

The researchers analyzed sandstone cliffs in the southwestern United States that are the remains of sand dunes from the Jurassic period.

Based on the orientations of the sediment layers within the rock, the researchers determined that the wind direction had remained generally constant in that area throughout the 100 million years of Pangea’s existence.

Because the wind directions on the continent should have changed as Pangea headed north, these findings raise the possibility that the continent instead remained at or near the equator.

These findings appear in the 23 November issue of the journal Science.

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