Occurs in the upper course of the river when weathering and mass movement occur on the valley sides, while the river erodes the base of the slope via vertical erosion (hydraulic action).
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How are graded stream profiles formed?
When a stream try's to adopt a concave, upward, long-profile by erosion, with steeper gradients found in the headwaters and gentler gradients as the stream approaches base level.
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How are waterfalls formed?
Occur on the margins of horizontally bedded bands of resistant rock underlain by less resistant rock. The less resistant rock erodes at a higher rate (via abrasion) causing the river to 'fall', over period of time plunge pool forms. High force, Tees.
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How are Gorges formed?
Once a waterfall forms, abrasion enlarges the plunge pool, the overhang becomes weak and falls into the plunge pool via gravity, over a period of time the waterfall retreats leaving a vertically sided channel called a gorge. Cheddar Gorge, Somerset.
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How do pot-holes form?
Formed by abrasion of pebbles held by turbulent flow and eddying of the stream. Giants kettle, Blyde river canyon, South Africa.
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Depositional landforms.
.
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How are braided channels formed?
When the river does not have the capacity to transport its load in a single channel, submerged bars and islands form via deposition, caused by a load that contains coarse material due to an easily eroded bank, highly variable discharge. White river.
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How do floodplains form?
High discharge due to high precipitation means the river flows out of its channel and onto the surrounding area, deposition occurs as velocity drops. Repetition over a period of time causes build up of alluvium that forms a floodplain. River Wye.
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How do levees form?
Formed by repeated river floods, causing its velocity to drop as floodwaters spill out of the channel, heaviest and coarsest sediment (sand) is deposited closest to the bank, over time raised banks form on the edge of the channel called levees.
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How do deltas form?
Deltas form when there are high levels of sediment at the mouth of the river, here the water is still meaning more deposition, additionally, the salt water causes salt particles to group (flocculation) Islands form. Mississippi River.
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Both erosional and depositional landforms.
.
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How do meanders form?
Development of pools and riffles cause the thalweg to flow from side to side, causing the river to flow laterally, this leads to erosion where the velocity is fast (causing pools) and deposition where it's slow (causing bars), horse shoe shape forms.
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How do oxbow lakes form?
The neck of land in a meander tightens due to the centrifugal force of water on the outer banks, the river then breaks through creating a new channel. The former meander is sealed off by deposition, leaving a oxbow lake. Reelfoot Lake, Tennessee.
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Other cards in this set
Card 2
Front
How are v-shaped valleys formed?
Back
Occurs in the upper course of the river when weathering and mass movement occur on the valley sides, while the river erodes the base of the slope via vertical erosion (hydraulic action).
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