Bedrock that has been pulverised at the bed of a glacier into clay- and silt-sized particles. The resulting sediment is commonly carried in suspension by glacial meltwater streams, which consequently take on a milky appearance (cf. glacier milk).
Rock flour deposited near the front of the glacier Kongsvegen, NW Spitsbergen, Svalbard. The muddy surface is desiccated and has the imprint of a polar bearís paws. Photo M. J. Hambrey.