By Sid Perkins
An unusual layer of rocks found along Britain’s northwestern coast formed from debris thrown out of a crater during a meteorite strike more than 1 billion years ago, geologists say.
The Stac Fada stratum, long thought to be of volcanic origin, stretches for 50 kilometers along the Scottish coast and in some spots is more than 20 meters thick.
“It was a puzzle,” says Kenneth Amor, a geologist at the University of Oxford in England. There are no similar strata elsewhere in the region, nor have any likely sources of volcanic material been found that match the stratum’s age.