Storms at the bottom of the sea.

Storms at the bottom of the sea

The dark abyss at the bottom of the ocean was thought to be quiet and almost totally at rest, with sediments slowly raining down and accumulating at a rate of about 1 millimeter per century. But photos taken in the 1960s shook that peaceful image by revealing signs that the sediments often shift position after they are on the bottom. Now, for the first time, scientists have observed the infrequent "storms" along the ocean floor that rearrange the sediments, report Thomas F. Gross of the Skidaway Institute of Oceanography in Savannah, Ga., and his colleagues in the Feb. 11 NATURE. Over the course of a year, meters stationed on the seafloor off Nova Scotia detected five occasions when currents at the bottom surged, sending the top millimeter of sediments awhirl. Photos from underwater cameras showed that these storms erased animal tracks and created ripple marks in the sediments.