Alaska's panhandle, the 500-mile-long sliver of coastal land that reaches southward between Canada and the Pacific, was once part of Australia.
That is the conclusion of a California Institute of Technology geologist who has analyzed a variety of clues in the land itself. His finding contributes to the rapidly growing body of evidence that continents are a mosaic of small pieces that formed in many now-separated locations.
Geologists know that land masses have been moving around the Earth for many hundreds of millions of years, breaking apart and rejoining many times.
About 250 million years ago most of the land coalesced into one supercontinent, called Pangaea. Since then, Pangaea has broken up, the major chunks wandering to their present locations.
Both before and after Pangaea existed, many smaller pieces have been drifting independently and sometimes sticking first to one continent and then being brushed off onto another.
According to the Caltech geologist, Jason Saleeby, the Alaskan panhandle formed about 500 million years ago as part of Australia. Then, around 375 million years ago, it broke off, drifted across the Pacific, stopped for a while off the coast of Peru and then, about 100 million years ago, collided with North America.
The evidence, published in Caltech's Engineering & Science magazine, comes from several sources. Radioactive dating of crystals in the panhandle's mountains show its rock formed when mountains were building in Australia, a time when North American mountains were dormant