Origin of rock flour
Examples from the Web for rock flour
Mountains were moved piecemeal, and ground to boulders, pebbles, and rock-flour in the moving.The Spell of the Rockies|Enos A. Mills
Nearly all of the soil in the Park is rock-flour that was ground by glaciers, and in part distributed by them.
Mountains are moved piecemeal, and are ground to boulders, pebbles, and rock-flour in the moving.