GEOMORPHOLOGICAL HAZARDS. Weathering & Mass Movement. WEATHERING : is the break down of a rock in the place where it is located due to contact with the weather. (It does not include the removal of the weathered material).
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GEOMORPHOLOGICAL HAZARDS Weathering & Mass Movement
WEATHERING: is the break down of a rock in the place where it is located due to contact with the weather. (It does not include the removal of the weathered material). EROSION: by the moving forces of ice, sea, winds and rivers involves wearing down and removal of the rock. DEFINITIONS
DENUDATION: is a term sometimes used to cover both processes and is particularly applicable when both are acting together & the junction between them is blurred.
WEATHERING • There are 2 main categories of weathering although some text books will use 3 categories as they include Biological as a separate weathering process although this is not strictly true. • The 2 main types are: • PHYSICAL (or Mechanical); rock disintegration without any change in chemical constituents. • CHEMICAL; some minerals either decay or alter due to some agent.
MECHANICAL WEATHERING • FREEZE-THAW (Frost Shattering). Ice occupies 9% more volume than the equivalent mass of water. Climate is the most important factor, temperatures need to vary between plus and minus. Scree slopes are a result of this process.
EXFOLIATION: in very hot arid areas with large diurnal temp changes causes rocks to expand during the day and the outer layers are pulled away from the cooler core as rocks are poor conductors of heat. At night as the temp falls the rock contracts. This causes the outer layers to peel away.
PRESSURE RELEASE • Rocks are under tremendous pressure so any slight change in pressure allows rocks to expand, so exfoliation occurs as this process creates joints near the surface of the rock, which can then be more vulnerable to further weathering process. Sugarloaf Mountain in Rio is an example of an exfoliation dome.
BIOLOGICAL: roots of plants and trees and the action of burrowing animals are capable of causing rock disintegration.