Weathering and the River Valley

Question 1

What is carbonation weathering(chemical)?

Answer 1

• Rainwater has carbon dioxide dissolved in it, creating a weak carbonic acid
• Carbonic acid reacts with rocks containing calcium carbonate so they are dissolved by rainwater

Question 2

What is biological weathering?

Answer 2

The breakdown of rocks by living things-plant roots break down rocks by growing into cracks on their surfaces and pushing them apart

Question 3

What does the profile of an upper course river cross section look like?

Answer 3

• Steep gradient
• V-shaped valley, steep sides
• Narrow, shallow channel

Question 4

What does the profile of a middle course river cross section look like?

Answer 4

• Medium gradient
• Gentle sloping valley sides
• Wider, deeper channel

Question 5

What does the profile of a lower course river cross section look like?

Answer 5

• Gentle gradient
• Very wide, almost flat valley
• Very wide, deep channel

Question 6

What is freeze-thaw weathering (mechanical)?

Answer 6

• Temp changes above and below 0 degrees
• Water gets into the cracks of a rock
• Water freezes and expands putting pressure on the rock
• Water thaws and contracts, releasing the pressure on the rock
• As this is repeated the cracks widen and cause the rock to break up