Why are glacial erratics found far from their source rocks?
Quick Answer
Glacial erratics are carried by ice for long distances and dropped when the glacier melts. They can sit on rock types very different from the ground beneath them.
The Full Story
As glaciers flow, they transport everything from fine sediment to enormous boulders. A rock picked up in one region may be embedded in the ice and carried tens or hundreds of kilometers before being deposited. Because the boulder can be unlike the local bedrock, geologists call it an erratic. These stones provide evidence of former ice-sheet movement and help reconstruct ancient glacial pathways. Famous erratics include boulders left by the Laurentide Ice Sheet in North America and across northern Europe.
Key Facts
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