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16 Terms
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Fluvial Processes
The processes that operate in rivers: EROSION (wearing away the land), TRANSPORTATION (carrying eroded material), and DEPOSITION (dropping eroded material). From source to mouth.
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Longitudinal Profile of a River
A visual representation (side view graph) of the gradient of a river from its source to its mouth. In theory, the shape is CONCAVE.
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Upper Course
The steep upstream section near the SOURCE of the river. Steep gradient, fast flow, vertical erosion, V-shaped valleys.
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Middle Course
Downstream of the upper course. The river leaves the mountains. Gradient is more gentle. Lateral erosion becomes dominant.
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Lower Course
The flat, final stage of the river as it approaches sea level. Deposition is the main process. Wide, flat valley.
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Base Level
The LOWEST level to which a river can erode. The SEA forms the permanent base level.
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Temporary Base Level
A feature that temporarily acts as a base level and prevents a river from eroding below it. Examples: a waterfall, a dam, a lake, rapids.
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Permanent Base Level
The sea / sea level — the absolute lowest level to which a river can erode.
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Hydraulic Action
Erosion process: the FORCE of flowing water loosens and removes pebbles, stones, sand and silt from the sides and bed of the channel (no tools needed — just the force of water).
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Abrasion (Corrasion)
Erosion process: sand and silt particles CARRIED by the river SCRATCH and WEAR AWAY the bed and sides of the channel (like sandpaper).
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Attrition
Erosion process: particles SCRATCH AGAINST EACH OTHER as they are transported, becoming SMALLER and ROUNDER (e.g. boulders → pebbles → sand).
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Solution (Corrosion)
Erosion process: soluble minerals in rocks are dissolved by the river water (chemical process).
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Traction
Transportation: BOULDERS and large rocks are PUSHED and ROLLED along the riverbed.
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Saltation
Transportation: smaller rocks and stones BOUNCE along the riverbed.
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Suspension
Transportation: SILT and very small particles are CARRIED within the flow of the water (float in the water).
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Solution (Transportation)
Transportation: load is DISSOLVED in the water (chemical change — invisible).