Soil Formation Notes

Soil

• The loose, weathered materials on Earth’s surface in which plants grow. • Soil is a mixture of rock particles,

minerals, decaying organic matter, water, and air.

Bedrock

• The solid layer of rock beneath the soil• When bedrock is exposed to Earth’s surface, it

weathers into soil

Humus

• Humus is the dark colored, decayed organic material in the soil.

Fertility

• Fertility is a measure of how well the soil supports plant growth

Loam

• Soil that is equal amounts of clay, sand, and silt is called loam.

LAYERS OF SOIL

Topsoil

• Topsoil is the top layer of soil. • Topsoil is also called the A Horizon of soil.• Topsoil is brown and crumbly, and is a mixture

of humus, clay, and minerals.

Subsoil

• Subsoil is made of clay and other particles that have been washed down from the A horizon.

• Subsoil is also called the B Horizon of soil.

C Horizon

• The C horizon contained partially weathered rock only.

Bedrock

• The bedrock layer is solid rock.