Soil as a system
•Soil is a complex plant-supporting system consisting of disintegrated rock, organic
matter, water, gases, nutrients, and microorganisms.
oFundamental to the support of life on this planet and the provision of food
fort he growing human population
•The composition of a region’s soil can have as much influence on the regions
ecosystems as do the climate, latitude and elevation.
•Soil is composed of living and non living components
Soil formation is slow and complex
•Parent material is the base of geological material in a particular location.
oCan include lava or volcanic ash; rock or sediment deposited by glaciers,
sediment doposited by rivers, or bedrock, the continuous mass of solid rock
that makes up Earth’s crust.
•Weathering, erosion, and the deposition of organic matter were responsible for soil
•Weathering describes the physical, chemical, and biological processes that breaks
down rocks and minerals, turning large particles into smaller particles.
•Physical Weathering or mechanical weathering breaks down rock without
triggering a chemical change in the parent material
oWind and rain are two main forces.
oAreas with extreme temperature fluctuations experience rapid rates of
oWater freezing and expanding in cracks in rock also causes physical
•Chemical weathering results when water or other substances chemically interact
with parent material.
oEg. Groundwater being unusually acidic.
•Biological weathering occurs when living things break down parent material by
physical or chemical means.
oTree accelerates weathering by physical action of its root growing and
rubbing against rock.
•Erosion is the movement of soil from one area to another