WEATHERING AND THE RIVER VALLEY

Rocks in a Dranage Basin are Broken Down by Weathering

Weathering happens in drainage basins-its the breakdown of rocks where they are (the material created doesnt get taken away like with erosion). There are three main types of weathering:

1) Mechanical weathering is the breakdown of rock without changing its chemical composition. Freeze-thaw weathering is a type of mechanical weathering it happens in drainage basins:

1) It happens when the temperature alternates above and below 0 degrees celcius (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 water thaws it contracts, which releases the pressure on the rock.

 5) Repeated freezing and thawing widens the cracks and causes the rocks to break up.

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