Ch.8 Weathering and Erosion

Weathering

is the physical disintegration and or the chemical decompostion of rocks at the Earth’s Surface that may result in the formation of sediments such as mud, sand, and gravel

Erosion

is the physical removal and transport of sediments by water, wind and ice

Differential Weathering

occurs when different minerals in the same rock weather at different rates

Mechanical Weathering

is the physical breakdown of rocks and minerals

Frost Wedging

is a type of mechanical weathering caused by the daily freeze thaw cycle and the expeansion and contraction of water

Salt Expansion

is a type of mechanical weathering that occurs when water evaporated, allowing salt crystals to grow within the cracks and fractures in rocks

Root Wedging

is a type of mechanical weathering that occurs when plant roots push rocks apart as they grow

Pressure Expansion

is a type of mechanical weathering that occurs when pressure is released from deeply buried rocks tat are uplifted to the surface

Sheeting

is the formation of onion like layers in granitic rocks due to pressure release and may result in Exfoliation such as Half Dome in Yosemite Valley

Spheroidal Weathering

is a result of the chemical weathering of the mechanically weathered joints and fractures in rocks

Chemical Weathering

is the chemical alteration or dissolving of minerals due primarily to acidic water (Carbonic Acid - H2CO3)

Oxidation

is a type of chemical weathering that occurs when iron atoms bond with oxygen atoms to form iron oxide

• Hematite, Goethite, Limonite

• Laterite Soil may form in very wet climates

Hydrolysis

is a type of chemical weathering that occurs when silicate minerals, like Feldspar, are chemically altered to form Clay minerals

Dissolution

is a type of chemical weathering that involves the dissolving of rocks and minerals by Carbonic Acid also known as Acid Rain

Soil

is an unconsilidated combination of air, water, minerals, clay and organic matter (humus) seperating the biosphere from the geosphere

O-Horizon

loose organic material, including humus at the Earth’s surface

A-Horizon

also called topsoil, includes humus, mineral sediment, and some leaching of soluble minerals

E-Horizon

is a zone of leaching found in very wet climates by the downward percolation of water

B-Horizon

also called subsoil, is a zone of humus accumulation from upper horizons and chemically weathered sediment; the upper portion is called regolith and the lower portion if called saprolite

C- Horizon

is a subtratum and a zone of mechanical weathering with no organic material present

R- Horizon

consists of unweathered, parent bed rock and fragments

Soil Classification

are classified by their morphology, behavior, genesis, and grain size

Bauxite (AI203)(H20)

is a mineral that forms when Laterite Soils are severely leached of silica and other soluble materials in a wet, tropical or subtropical climate