Ancient Dunes Preserve Signs of Dinosaur-Shaking Earthquakes

Long ago, when the Earth had only one continent and one ocean, an earthquake rippled through western North America's great sand sea. The early Jurassic earthquake left its mark in the vast dunes that now form the famous red cliffs of Zion National Park in Utah, a new study finds.

The seismic waves violently shook the water-saturated ground beneath the giant dune field, sending liquefied sand spurting up through the dunes like a volcano, researchers believe. Some 180 million years later, these sand blowouts, which look like cylindrical pipes, were discovered in the Navajo Sandstone.

The sandstone is so finely bedded that the researchers can identify cyclic patterns, such as summer and winter layers. At one spot in Zion National Park, lead study author David Loope and his colleagues picked out a yearlong sequence of sand pipes

http://www.livescience.com/39117-nav...arthquake.html