Denudation
Denudation is an erosive process of breaking and removing the rocks from the surface of the earth. It is the wearing away of the terrestrial land by weathering, erosion, moving water, ice waves. Denudation is the result of two main processes, Endogenous and exogenous.
Differential weathering
-differential weathering. noun Geology. the difference in degree of discoloration, disintegration, etc., of rocks of different kinds exposed to the same environment
weathering factor: Bedrock
Rock composition and structure
weathering factor: Joints
Joints are fractures or separations in rock that occur without displacement of the sides.
The presence of joints increases both physical and chemical weathering. Why? It increases the surface area of rock exposed to both physical and chemical weathering.
weathering factor: geographic orientation
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weathering factor: climate
Precipitation, temperature, and freeze–thaw cycles
Physical weathering dominates in drier and cooler climates.
Chemical weathering dominates in wetter and warmer climates
weathering factor: vegetation
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Physical Weathering: Frost Action,
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Physical Weathering: Crystallization
As the water on the surface of rocks evaporates, dissolved minerals in the water grow crystals—crystallization. Over time, as the crystals grow and enlarge, they exert a force to spread apart individual mineral grains and begin breaking up the rock.
Physical Weathering: Talus slopes
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Physical Weathering: Hydration
Hydration and hydrolysis, chemical weathering processes involving rocks interacting with water, contribute to flared slopes, sometimes nicknamed “wave rocks.” Their c-shape is largely a result of subsurface weathering, in which hydration and hydrolysis decompose rocks beneath the landscape’s surface.
Physical Weathering: Exfoliation
Erosion removes mass
Isostatic rebound
Sheets of rock discarded
Physical Weathering: Sheeting
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Physical Weathering: Pressure release jointing
pressure-release jointing. [′presh·ər ri¦lēs ‚jȯint·iŋ] (geology) Exfoliation that occurs in once deeply buried rock that erosion has brought nearer the surface, thus releasing its confining pressure.
Chemical Weathering: Spheroidal Weathering
Spheroidal weathering is a form of chemical weathering that affects jointed bedrock and results in the formation of concentric or spherical layers of highly decayed rock within weathered bedrock that is known as saprolite.
Chemical Weathering: Hrdolysis
the chemical breakdown of a compound due to reaction with water.
Chemical Weathering: Carbonation and solution
The limestone solution process is also known as carbonation. Limestone is made of calcium carbonate. When carbon dioxide is dissolved in rainwater, it makes a weak acid called carbonic acid.
Mass Movement Processes:
Mass movements can be divided into four main classes. These are falls, slides, creeps and flows. The classes are based on how quickly the rock and sediment moves and how much water there is. Steep and unstable slopes are more likely to have a mass movement than gentle and stable slopes.
Mass Movement Processes: Role of slopes
Weathering loosens material, making it more susceptible to erosion and transportation.
For material to move downslope, the forces of erosion must overcome other forces: friction, inertia (the resistance to movement), and the cohesion of particles to one another.
If the angle is steep enough for gravity to overcome frictional forces, or if the impact of raindrops or wind dislodges material, then erosion of particles and transport downslope can occur.
Mass Movement Processes: angle of repose
The angle of repose, or critical angle of repose, of a granular material is the steepest angle of descent or dip relative to the horizontal plane to which a material can be piled without slumping. At this angle, the material on the slope face is on the verge of sliding. The angle of repose can range from 0° to 90°.
Mass Movement Processes: Falls and avalanches, Landslides
Landslides are large masses of wet or dry rock and soil that fall, slide, or flow very rapidly under the force of gravity. Landslides commonly originate as massive rock falls or avalanches, which disintegrate during movement into fragments ranging from small particles to blocks hundreds of meters across.
Flows, Creep
Creeps. Soil creep is a slow and long term mass movement. The combination of small movements of soil or rock in different directions over time are directed by gravity gradually downslope. The steeper the slope, the faster the creep.
