Soil Formation and Earth's Surface

Soil Formation

The weathering of rocks

Mosses and lichens are called pioneer organisms because they are the first organisms to grow on rocks

the addition of humus (decaying organic matter)

A soil profile is a cross section of soil.

There are three major soil horizons – A, B, and C.

top & darkest layer (high concentration of organic matter - humus)

Top soil

subsoil enriched with clay minerals leached from the topsoil.

bottom layer (weathered rock)

Parent Rock

Topography (slope) of the land – Soils on slopes tend to be thinner soils in flat areas like valleys or plains are thicker

Age – older soils are thicker because they have had more time to develop.

Climate

Distribution of Soil Types

Particles of soil are classified by size.

The particles of soil are clay, silt, & sand.

What determines a soil’s texture?

The relative proportions of these particles.

The texture of a soil affects its capacity to absorb and retain water & support plant growth.

Soil Texture Triangle