Sand, gravel, and other sediment
Sediment is material eroded off other rocks that is then worn down into pieces ranging in size from microscopic particles to pebbles to boulders. It is often carried from its source—the rock or mineral deposit it was eroded from—by wind or water and deposited in other areas, sometimes hundreds of miles away.
Many sedimentary rocks are formed when layers of sediment are buried under more layers of sediment and then pressed together by the weight from above. Sometimes, the sediment is cemented by minerals and other materials.
Common sediments in Kansas:
- Sand—rock fragments or mineral particles that range in diameter from about 1/16 to 2 mm (from 0.002 to 0.08 inches).
- Gravel—chipped or rounded rock fragments that typically range in diameter from about 3 to 75 mm (0.125 to 3 inches).
- Clay—a very fine grained material composed mainly of flakes from a variety of minerals weathered off rocks and mineral deposits. Clay particles are microscopic in size (less than 1/256 mm, or 0.00015 inches, in diameter).
- Loess—nonstratified (not divided into layers) sediment composed of silt-sized particles deposited by the wind. These windblown dust deposits were often derived from glacial materials. Loess is found throughout Kansas but is especially common in the northeastern and northwestern parts of the state. The particles are microscopic in size.
- Volcanic ash—fine rock material formed by volcanoes. Volcanic ash deposits in Kansas were carried by wind from eruptions from the western United States. Volcanic ash particles are less than 2 mm, or 0.08 inches, in diameter.
- Alluvium—unconsolidated clay, silt, sand, or gravel deposited during recent geologic time by running water in the bed of a stream or on its floodplain.
Buchanan, R., 2010, Kansas Geology: An Introduction to Landscapes, Rocks, Minerals, and Fossils (2nd ed.): Lawrence, Kansas, University Press of Kansas, 240 p.
Buchanan, R., and McCauley, J. R., 2010, Roadside Kansas: A Traveler's Guide to Its Geology and Landmarks (2nd ed.): Lawrence, Kansas, University Press of Kansas, 392 p.
Kansas Rocks and Minerals, Kansas Geological Survey Educational Series 2