Key Terms:  alluvium - generally a waterborne material deposited on bottomlands, such as deltas and flood plains. bedrock - the native consolidated rock. chemical weathering climate - rainfall glacier - a large, long-lasting river of ice that is formed on land and moves in response to gravity. glacial till - often contains soil particles of many sizes. loess - soil moved and deposited by wind. native vegetation - This vegetation determines the kind and amount of organic matter in the soil. organic soils - occur where formerly shallow ponds supported swamp vegetation. outwash - formed when the glaciers melted. parent materials - formed by the disintegration and decomposition of rock. physical weathering - effects of climatic factors, such as temperature, water, and wind. prairie soil - has a dark and deep surface layer. timber soil - tends to have a thin, moderately dark layer. topography - the slope characteristics of a soil. Checking Your Knowledge:  1. What are parent materials? Parent materials are formed by the disintegration and decomposition of rock. 2. What types of soils have a glacial origin? Outwash soils have a glacial origin. 3. How does topography affect soil formation? Topography is the slope characteristics of a soil. 4. How do living organisms affect soil formation? This vegetation determines the kind and amount of organic matter in the soil. 5. What influence does weathering have on soil formation? Weathering causes soil to develop, mature, and age.