Weathering and Soil

weathering

wearing away of rocks into smaller pieces

physical weathering

the mechanical breakdown of rocks and minerals

frost action

the weathering of rock by repeated freezing and melting of water

root wedging

when the roots of plants grow and search for minerals and water in rock fractures, exerting pressure on the rocks and driving them apart

abrasion

The grinding away of rock by other rock particles carried in water, ice, or wind

oxidation

A chemical change in which a substance combines with oxygen, as when iron oxidizes, forming rust

acid rain

Rain containing acids that form in the atmosphere when industrial gas emissions (especially sulfur dioxide and nitrogen oxides) combine with water.

Hydrolysis

Breaking down complex molecules by the chemical addition of water

soil horizon

The layer of soil that differs in color and texture from the layers above or below it.

soil profile

All the vertical layers or horizons that make up a soil in a particular place

A-horizon

topsoil

B-horizon

A soil horizon composed primarily of mineral material with very little organic matter

C-horizon

The least-weathered soil horizon, which always occurs beneath the B horizon and is similar to the parent material.

humus

material formed from decaying leaves and other organic matter

soil

A loose mixture of rock fragments, organic material, water, and air that can support the growth of vegetation

soil formation

Soil forms as rock is broken down by weathering and mixes with other materials on the surface.

parent material

the rock material from which the inorganic components of a soil are derived

residual soil

Soil that remains above its parent rock

transported soil

Soil that has been moved away from its parent material by water, wind, or a glacier.

particle size

the smaller the particle the faster the chemical reaction

climate

The average weather conditions in an area over a long period of time