: Paléoclimatologie: glacial flour

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glacial flour

Rock flour, or glacial flour, consists of fine-grained, silt-sized particles of rock, generated by mechanical grinding of bedrock by glacial erosion or by artificial grinding to a similar size. Because the material is very small, it becomes suspended in meltwater making the water appear cloudy, which is sometimes known as glacial milk. Typically, natural rock flour is formed during glacial migration, where the glacier grinds against the sides and bottom of the rock beneath it, but also is produced by freeze-and-thaw action, where the act of water freezing and expanding in cracks helps break up rock formations. Multiple cycles create a greater amount. Although clay-sized, the flour particles are not clay minerals but typically ground up quartz and feldspar. Rock flour is carried out from the system via meltwater streams, where the particles travel in suspension. Rock flour particles may travel great distances either suspended in water or carried by the wind, in the latter case forming deposits called loess. (Adapted from: https://en.wikipedia.org/wiki/Rock_flour)

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