WATER ON THE LAND
- Created by: Georgia Barnaby
- Created on: 01-05-14 17:44
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- WATER ON THE LAND
- A river is usually split into three courses: upper, middle and lower course.
- Upper course: narrow valley with steep sides. Waterfalls and rapids. Velocity is low because high friction. Vertical corrosion in upper course.
- Middle course: valley is wider with more gentle slopes. Greater velocity with lateral (and some vertical) erosion occurring. Meanders and oxbow lakes.
- Lower course: wide valley, extremely gentle slopes. Velocity can be lower than middle course (low gradient). flood plains (with alluvium) and levees. Deposition key process.
- Rivers can be looked at in either long profile or cross profile diagrams.
- Long profile shows river from source to mouth. Shows the gradient if the river. Split into the three stages. Normal shape is concave and with a decreasing gradient.
- Cross profile shows a view across the river and valley. For example, more of a V shape in the upper stage, but gets wider and flatter in lower stages.
- Rivers erode in 4 main ways.
- Hydraulic action: the force of the water against the rocks.
- Corrosion: dissolving of the rocks through a chemical reaction.
- Abrasion: when the river bashes against the bed with it's load.
- Attrition:when the boulders and sediment bash into each other.
- Rivers transport material in 4 ways.
- Traction: when boulders roll along the bottom of the river bed.
- Saltation: when boulders bounce along the bottom of the river bed.
- Suspension: some material is light enough to be carried along in the current.
- Solution: when the material dissolves in the water (for example calcium carbonate)
- Features of rivers include waterfalls, gorges, meanders, levees and oxbow lakes.
- Waterfalls forms due to differential erosion. Plunge pool created. Gorge formed as waterfall retreats.
- Meanders are thought to form due to a series of riffles and pools (shallows and deeps). Cause uneven flow, therefore erosion and deposition occur, causing bend.
- Oxbow lake forms when the loop of a meander becomes bigger and the neck smaller. A river cliff develops on outside, slip off slope on inside bend.
- Levees are natural embankments that develop on the bank of the river when the river has flooded.As velocity decreases, it deposits material forming the levee.
- A river is usually split into three courses: upper, middle and lower course.
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