Waterfalls

Question 1

Explain how a waterfall is formed

Answer 1

1) erosion erodes the river bed in the upper course
2) soft rock erodes quicker that hard rock
3) over time, the soft rock is eroded which undercuts the hard rock leaving an overhang
4) underneath the overhang a plunge pool is formed by the hydraulic action of the water flowing over the overhang
5) the overhang collapses into teh plunge pool
6) the material that has collapsed into the overhang erodes the plunge pool by abrasion making it larger
7) over time the waterfall will retreat up the river valley as the cycle of erosion continues
8) a steep sided gorge is left behind in the river valley as the waterfall retreats

Question 2

Abrasion

Answer 2

When pebbles grind along the river bank and bed and wear it away like sandpaper

Question 3

Attrition

Answer 3

When rocks knock against eachother and break down to become smaller

Question 4

Solution

Answer 4

When water dissolves certain types of rock like limestone

Question 5

Hydraulic action

Answer 5

The power of water as it smashes against the river banks. Air becomes trapped in the cracks which causes the rock to break apart