WEATHERING & THE RIVER VALLEY.
- Created by: chelsie webb
- Created on: 12-08-13 15:00
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- WEATHERING & THE RIVER VALLEY.
- WEATHERING:
- FREEZE-THAW WEATHERING: mechanical weathering that happens in a drainage basin
- 1)happens when the temperature alternates above and below 0 degrees Celsius (the freezing point of water)
- 2)Water gets into rock that has cracks, e.g. granite
- 3)When the water freezes it expands, which puts pressure on the rock
- 4)When the water thaws, it contracts, which releases the pressure on the rock.
- 5)Repeated freezing and thawing widens the cracks and causes the rock to break up.
- MECHANICAL WEATHERING: breakdown of rock without changing its chemical composition
- FREEZE-THAW WEATHERING: mechanical weathering that happens in a drainage basin
- CHEMICAL WEATHERING: breakdown of rock by changing its chemical composition
- CARBONATION WEATHERING: chemical weathering that happens in warm and wet conditions:
- rainwater has carbon dioxide dissolved in it, which makes it a weak carbonic acid.
- carbonic acids react with rock that contains calcium carbonate, e.g. limestone,so the rocks are dissolved by rainwater
- BIOLOGICAL WEATHERING: breakdown of rocks by living things, e.g. plant roots break down rocks by growing into cracks on their surfaces and pushing them apart
- FREEZE-THAW WEATHERING: mechanical weathering that happens in a drainage basin
- THE RIVER VALLEY
- COURSE: the paths of a river as it flows downhill
- Rivers flow in channels in valleys.
- They erode the landscape- wear it down, then transport the material to somewhere else where its deposited
- The shape of the valley and channel changes along the river depending on whether erosion or deposition is having the most impact.
- LONG PROFILE: shows how the gradient (steepness) changes over the different courses.
- CROSS PROFILE: shows what a cross-section of the river looks like
- UPPER COURSE:
- GRADIENT: steep.
- VALLEY AND CHANNEL SHAPE: V-shaped valley, steep sides, narrow, shallow channel
- MIDDLE COURSE:
- GRADIENT: medium
- VALLEY AND CHANNEL SHAPE: gently sloping valley sides, wider, deeper channel
- LOWER COURSE:
- GRADIENT: gentle
- VALLEY AND CHANNEL SHAPE: very wide, almost flat valley. very wide, deep channel.
- WEATHERING:
- BIOLOGICAL WEATHERING: breakdown of rocks by living things, e.g. plant roots break down rocks by growing into cracks on their surfaces and pushing them apart
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