Geography Chapter Notes
Chapter 15 Outline * Soil is the relatively thin surface layer of Earth’s crust consisting of minerals and organic matter modified by natural actions like… * Weather * Wind * Water * Organisms * Soil is formed from parent material, rock that is slowly broken down or fragmented into smaller particles by… * Weathering Processes
Biological
* Chemical * Physical * Topography, a region’s surface features such as the presence or absence of mountains and valleys, is also involved in soil formation. * Soil Composition: soil is composed of 4 distinct parts, minerals that make up 45% of a soil. * Organic Material (5%) * Water (25%) * Air (25%) * Mineral portion which comes from weathered rocks provides anchorage and pore space for air and water. * Age affects mineral composition * Australia, South America, India have old infertile soil * Litter (dead leaves and branches on the soils surface) * Humus: Black or dark brown organic material that remains after decomposition has occurred. * Illiviation: The deposition of leached material in the lower layers of soil * Soil Horizons: * O-horizon (accumulation of plant litter) * A-horizon (accumulation of organic matter of humus) * E-horizon (heavily leached) * B-horizon (accumulation of clay and nutrient materials) * C-horizon (weathered pieces of rock) * Solid Parent Material (bedrock) * Soil Organisms: * Ecosystem Services: maintaining soil fertility * Castings: bits of soil that have passed through the gut of an earthworm are deposited at the soil’s surface. * Mycorrhizae: helps plants absorb adequate amounts of essential nutrient minerals. * Mycelium: fungal threadlike body
* Soil Texture refers to the relative proportions of different sized inorganic mineral particles of sand, silt, and clay. * Sand-largest soil particle
Biological
* Chemical * Physical * Topography, a region’s surface features such as the presence or absence of mountains and valleys, is also involved in soil formation. * Soil Composition: soil is composed of 4 distinct parts, minerals that make up 45% of a soil. * Organic Material (5%) * Water (25%) * Air (25%) * Mineral portion which comes from weathered rocks provides anchorage and pore space for air and water. * Age affects mineral composition * Australia, South America, India have old infertile soil * Litter (dead leaves and branches on the soils surface) * Humus: Black or dark brown organic material that remains after decomposition has occurred. * Illiviation: The deposition of leached material in the lower layers of soil * Soil Horizons: * O-horizon (accumulation of plant litter) * A-horizon (accumulation of organic matter of humus) * E-horizon (heavily leached) * B-horizon (accumulation of clay and nutrient materials) * C-horizon (weathered pieces of rock) * Solid Parent Material (bedrock) * Soil Organisms: * Ecosystem Services: maintaining soil fertility * Castings: bits of soil that have passed through the gut of an earthworm are deposited at the soil’s surface. * Mycorrhizae: helps plants absorb adequate amounts of essential nutrient minerals. * Mycelium: fungal threadlike body
* Soil Texture refers to the relative proportions of different sized inorganic mineral particles of sand, silt, and clay. * Sand-largest soil particle