Soil 6 th grade Earth Science Howard Middle School

Soil  Soil is defined as the layer of unconsolidated material found at the earth’s surface.  Soil thickness varies from a few millimeters (mm) to several meters (m).

Soil  Thinner soils can indicate a very young soil or a place where soil has been removed by water, wind, gravity, or animal activity.

Composition  Weathered mineral particles  Dead and living organic matter  Dissolved substances

Composition  The type of soil that exists in an area is influenced by five major factors: Local climate Topography Rock types Organisms (especially plants) Amount of time the soil has been developing

Classifying Soils  In general, soils are classified based on the proportion of organic material and the different-sized particles—sand, clay, and silt—that they contain.

Inorganic and Organic Components  The size and type of the inorganic components of a soil are determined mostly by the local rock type and terrain.  The type and amount of organic material is influenced mostly by climate (temperature, sunlight, and precipitation).

Dead and Living Organic Material  Dead organic material is particularly important because it contains a readily accessible source of necessary nutrients.  Living organic material helps aerate the soil and decompose the dead material.