Lecture 8 Weathering and Erosion

Weathering

Disintegration of rock at or near the earths surface

Mass wasting

Transfer of material downslope in response to gravity

Weathering

Disintegration of rock at or near the earths surface

Mass wasting

Transfer of material downslope in response to gravity

Erosion

Transport of material by mobile agents

Wind, water, ice

Exfoliation

• Concentric or spherical shells of decayed rock are successively separated from a block of rock

• Horizontal fracturing due to release of pressure

• Commonly results in the formation of a rounded boulder of decomposition

Factors that impact mechanical weathering

• Temperature

• Frost heaving

• Frost wedging

• Water action

Frost heaving

Ice forming beneath the surface of soil during freezing conditions in the atmosphere

Frost wedging

Water action

Causes pot holes

Hydrolysis

occurs especially with granite, causes rock to whiten (erodes slowly), and creates clay.

Oxidation

occurs especially with rock containing iron nitrate,  creates rusty red rock, and erodes and forms soil.

Hydration

a physio-chemical process in rocks containing salt minerals.

Chemical weathering

The alteration of the internal structure of minerals by chemical reactions

Carbonate dissolution

Ground water forms with carbon dioxide to form a slightly acidic solution

Lichens

• make your skin irritated and itch

• Grow on rocks and produce weak acids that chemically weather rocks

Erosion by water

The process by which water, ice, wind, or gravity moves fragments of rock and soil

Erosion by ice glaciers

Wind erosion

What is soil

• The layer of rock and mineral fragments along with organic matter, water and air supports the growth of plants

• Thin layer of material covering the earth ‘s surface and formed from weathering of rocks

Talik

Layer of year round unfrozen ground that lies in permafrost areas

Soil profiles by biome