SOIL Composition Formation Erosion Profile Soil Composition Soil

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

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

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