A glacial dropstone (center of photo) is exposed in a well-bedded Pleistocene glacial clay deposit along a cutbank of the North Fork Skykomish River. The dropstone was likely entrapped in an iceberg that was ice-rafted into a glacial lake. After the dropstone fell from the iceberg to the bottom of the lake, the dropstone was buried in the fine-grained lake sediment. Notice that the clay beds beneath the stone are slightly deformed (pressed down) due to the weight of the stone. As clay deposition continued, draped layers formed over the dropstone.
North Fork of the Skykomish River, near Index, Washington, USA
Photo Copyright © 2009 Jeffrey M. Schwartz