Download 7th grade Soil Notes

Soil Notes: It isn’t just dirt!
*Formation: Soil is formed when rocks are continuously broken down by weathering.
Residual Soil: Soil that has a composition similar to its parent rock; soil that formed where it is
located.
Transported Soil: Soil that has been moved away from its parent rock by erosion and deposited
somewhere else.
Bedrock (Parent rock): Layer of rock below the soil.
Humus: Decaying organic material found in the topsoil layer.
*Composition: The main ingredients of any particular soil.
Weather rock and organic material are the two main ingredients of soil.
*Clay and quartz are the most abundant materials.
Potassium, phosphorous and nitrates are the most common minerals
*Humus is very rich in minerals that help plants grow, but remember plants do not
require soil to grow…just water, sunlight and CO2
*Air and water fill pore spaces. Plants use this air and water.
*The type of weathering affects soil composition.
*Soil texture is the size of the soil particles; determined by weathering.
*Soil Horizons: Distinct, separate layers of soil that form over time.
Soil Profile: Cross section of soil horizons.
Mature Soil: Soil with three well-developed layers.
A Horizon or Topsoil: Mostly humus and organic material.
B Horizon or Subsoil: Mostly clay, some humus and other minerals.
C Horizon: Mostly weathered rock with the same composition as the parent rock.
Parent Rock: Original material.