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23 Cards in this Set
- Front
- Back
What are the four types of erosion?
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-Hydraulic action (the force of the water breaks up rocks)
-Abrasion -Attrition -Solution (river dissolves some rock particles) |
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What are the four types of transportation?
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-Traction
-Saltation -Suspension -Solution |
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What are some reasons that a river may slow down and deposit material?
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-The volume of water decreases
-The river reaches its mouth -The water is shallower |
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What does vertical erosion do and in which course of the river is it most dominant?
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It deepens the the river valley (and channel) making it v-shaped, most dominant in the UPPER course.
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What does lateral erosion do and in which courses of the river is it most dominant?
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It widens the river valley (and channel), most dominant in MIDDLE AND LOWER courses.
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In which courses of a river would you find a meander?
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MIDDLE AND LOWER courses
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How is a meander formed?
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Current is faster on outside of the bend, so more erosion there, forming RIVER CLIFFS
Current is slower on the inside, so more deposition there, forming SLIP-OFF SLOPES |
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How is an ox-bow lake formed?
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-formed from meanders
erosion causes the outside bends to get closer until it gets to a point were there's only a bit of land land between the bends (the neck), which the water eventually breaks through. Deposition cuts off the meander to form an ox bow lake |
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In which course of a river would you find waterfalls and gorges?
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the UPPER course
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By which process are waterfalls and gorges formed?
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Erosion
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How is a waterfall formed?
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when a river flows over hard rock, then soft rock, the soft rock is eroded more, making a 'step' in the river, and as erosion continues on the area of soft rock, it eventually creates a STEEP DROP, ie. a waterfall
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How is a gorge formed?
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continues on from a waterfall, the hard rock is eventually undercut by erosion and collapses. a plunge pool is formed (in the soft rock) by abrasion as the collapsed rock swirls around, then more undercutting, so more collapses, and the waterfall retreats, leaving a steep sided gorge
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By which process are flood plains and levees formed?
Which course of the river are they both found in? |
Deposition
the LOWER course |
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How is a flood plain built up? (it already exists on either side of a river)
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-when a river floods onto the plain, the water slows and it DEPOSITS the material its been transporting, making it HIGHER
-meanders migrate across the plain to make it WIDER -the deposition on slip-off slopes of meanders, make it HIGHER |
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How are levees formed?
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During a flood, eroded material is deposited over the whole flood plain, heaviest material is deposited closest to the river channel. After repeated flooding, THE DEPOSITED MATERIAL BUILDS UP, creating levees.
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Define river discharge.
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The VOLUME of WATER flowing in a river per second
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What are the physical factors that can cause a river to flood?
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-Prolonged rainfall
-Snowmelt -Heavy rainfall -Relief (how the height of the land changes) |
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What are the human factors that can cause a river to flood?
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-Deforestation
-Urbanisation (building construction) -> impermeable surfaces that are built - buildings and roads - increase surface runoff and drains quickly take runoff to rivers. This increases discharge quickly, which can cause a flood |
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Define watershed
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An area of land that contains a common set of streams and rivers that all drain into a single larger body of water (a drainage basin)
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Define confluence
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The meeting of two or more bodies of water
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Define tributary
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A river or stream that flows to a larger body of water, eg another river
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Define source
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Where a river starts
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Define mouth
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The end of the river when it joins a larger body of water, eg. the sea
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