GEOL 1 Lecture Notes - Lecture 27: Soil Liquefaction, Soil Retrogression And Degradation, Calcite
Jeff Koo
Geol 1
Physical Geology
Spring 2019
4 Units
Soils and Subsidence and Sinkholes
● Soils
○ Weathered rock and organic material [organic material = decomposed plant and
animal remains]
○ Comprised of different layers or horizons
○ Although soil may be eroded and transported elsewhere, all layers initially form
together in place
● Importance of soils
○ Life, including ours, depends on soil
○ Agriculture can be greatly diminished through soil degradation and loss
○ Soil types and properties must be considered when building
○ Soil characteristics important for determining landslide and earthquake
liquefaction risks
○ Soil behavior itself may present hazards
● Soil horizons
○ O - organic material
○ A - topsoil
○ B - subsoil
○ C - weathered bedrock
○ R - residual bedrock
● Soil erosion
○ Generally by water and wind
○ Becomes a hazard when rate of erosion exceeds rate of formation
○ Loss of farm topsoil a growing problem worldwide
● Aggravation
○ Soil erosion can be greatly accelerated by
■ Drought
Document Summary
Weathered rock and organic material [organic material = decomposed plant and animal remains] Although soil may be eroded and transported elsewhere, all layers initially form together in place. Agriculture can be greatly diminished through soil degradation and loss. Soil types and properties must be considered when building. Soil characteristics important for determining landslide and earthquake liquefaction risks. Becomes a hazard when rate of erosion exceeds rate of formation. Loss of farm topsoil a growing problem worldwide. Soil erosion can be greatly accelerated by. Overgrazing (too much livestock eating the crops) Causes building challenges and damage where it is present. Groundwater withdrawal for agriculture caused significant subsidence in. May cause areas to be more prone to flooding. Usually in carbonate rocks (made of mineral calcite) Usually triggered by natural processes but may be aggravated. Co2 in atmosphere forms carbonic acid in rain and snow.
