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Rivers & Coasts (Features of river basin (area of land drained by a…
Rivers & Coasts
Features of river basin
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flood plain = flat land in lower course of river, likely to flood
The estuary is a wide area near the mouth of the river where the sea water mixes with fresh water, forming brackish water.
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At this point, the river drops much of the load it has been carrying, which sometimes forms a delta.
Types of weathering
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Biological Weathering
- This process is caused by plants and animals.
- Burrowing animals break up the rocks.
Plant seeds fall into cracks and germinate, breaking up the rocks.
- Tree roots grow into cracks in the rocks and then exert pressure on the cracks as they grow, causing them to widen.
Chemical Weathering
- This process is caused by rain, which contains carbonic acid.
- The acid in the rain attacks the rock, causing it to crumble.
Sedimentary rocks, such as limestone and chalk, are particularly vulnerable to this type of weathering.
As the carbonic acid falls on limestone, it turns it into calcium bicarbonate, which is soluble in water.
Limestone gravestones are commonly attacked and limestone pavements are also vulnerable as the acid water can seep into deep cracks and attack a large surface area.
Rock Types
Igneous
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if reaches to earth's surface = lava, once cooled, formed by basalt
Sedimentary
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sink into the sea bed, then form to rock after millions of years by being compressed
Metamorphic
made by igneous or sedimentary rock after being exposed to pressure or heat during the earth's movements
eg, chalk & limestone = marble clay = slate
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