Rock Flour
U.S. Geological Survey photo by Bruce Molnia (fair use policy)
Glaciers grind their rocky beds exceeding small, and the smallest particles reach clay size, the consistency of flour. Rock flour is quickly altered to actual clay minerals. Here two streams in Denali National Park merge, one full of glacial rock flour and the other pristine.
The rapid weathering of rock flour, coupled with the intensity of glacial erosion, is a significant geochemical effect of widespread glaciation. In the long term, over geologic time, the added calcium from eroded continental rocks helps pull carbon dioxide from the air and reinforces global cooling.
Fossils
Geologic Features and Processes
Glaciers and Ice
Landforms
Minerals
Rocks
Geology and Society
