Weathering Flashcards
Types of weathering
Mechanical, chemical, biological
Mechanical weathering
The physical break up of rocks composition. It can be caused by rocks having zones of weakness along which they break, or temperatures fluctuate above and below freezing forcing rocks to crack.
Increase in surface area ____ chemical weathering
increases
Chemical weathering
The breakdown of minerals by chemical reaction with water or gases in either the atmosphere or pore-waters.
Chemical weathering is dependant on what factors
- Parent material and 2. Climate
Parent material influence on weathering
mineral differ in the kinds of different chemical reactions they undergo. High temperature formed minerals are less stable, while secondary minerals are more stable.
Minerals with the fastest rate of weathering due to chemical weathering
Olivine (formed at high temperatures), calcite and halite (an evaporite)
Most stable minerals from chemical weathering
iron oxides, aluminum hydroxides, and quartz
Chemical weathering reaction
Water combines with carbon dioxide (H2O and CO2 combine to make H2CO3) and dissociate to make H ion and HCO3 ion. Carbonate ion and H ion combines with other minerals to form clays.
Climate effect on Chemical Weathering
Since chemical reactions require water, the more water, the more intense the chemical weathering. Also, most chemical reactions proceed more rapidly at high temperatures than colder temperatures.
Regolith
loose material on top of bedrock, consisting of minerals, organic material, and microorganisms, air, and water.
A measure of weathering is seen in the thickness of the ____.
Regolith
Examples of biological weathering
mechanical (tree roots in splitting rocks apart) and chemical (organic acids produced)
The most important biological weathering reaction is from the _____.
Aerobic respiration of dead organic matter.
The oxidation reaction of aerobic respiration
C6H12O6 +O2 —> 6CO2 + 6H2O
formation of carbonic acid
mixing CO2 and water, 6CO2 + 6H2O –> H2CO3
Dissociation of Carbonic acid
produces bicarbonate and protons (acid)
H2CO3 –> H + HCO3
Erosion
Erosion is the action of surface processes that removes soil, rock, or dissolved materials from one location on the Earth’s surface, and then transports it to another location.
Methods of transport in erosion
gravity, water, ice and wind
Colluvium
Material that accumulates at the bottom of landslides due to erosion transport by gravity
Transportation by water deposits (erosion)
alluvium (river), lacustrine (lake), and marine (oceans)
Transportation by Ice (erosion)
As the glacial ice advances, the underlying soils and rock are removed and eroded. As the ice melts and the glacier retreats, the glacial debris/drift (till) remains and provides a new source of material for soil formation.
Transportation by wind
Deposits are called eolian deposits and are formed via the accumulation of wind-blown dust.
Loess deposits
Wind-blown dust derived from glacial material, composed primarily of silt and clay
