Composition Formation Erosion Profile SOIL Composition Formation Erosion Profile

Soil Composition Soil is a mixture of . . . Humus (decaying organisms) Sediment (weathered bits of rock; determines soil texture) Water Air 50% solids, 25% liquid, 25% gases/pore spaces

Soil Formation Humus: from the decay of organic matter Vegetation Animals Fungi

Soil Formation Sediment: from the weathering of rock Bedrock—weathers at location of soil formation Regolith—loose rock on top of bedrock Sediment—brought in from another location via erosion

Rate of Soil Formation Factors that speed/slow soil formation: Hardness of parent rock: lower = faster Time: more = more Slope: steeper = faster Vegetation: more = faster Animals: more = faster CLIMATE (most important): wetter = faster

Rate of Soil Erosion Increases dramatically with the amount of people in an area Activities that increase soil erosion: Farming Logging Roads Removing vegetation

O A E B C R Soil Profile …is a group of soil horizons (layers) O: humus A: sediment & humus mix E: minerals leach out of sediment & seep down B: seeped minerals from horizon E collect here C: partially weathered bedrock R: unweathered bedrock

Soil Texture Activity

Soil Texture Activity Loam — mixture of sand, silt, and some clay Texture is rough & spongy Ideal for plants - Enough porosity for roots to get air without losing all water & nutrients