formations

Question 1

waterfall*

Answer 1

• differential erosion takes place. Hydraulic action (desc) erodes the soft rock and undercuts the hard rock
• an overhang is created which is unsupported and collapses over time due to gravity
• a plunge pool forms at the base of the waterfall caused by abrasion (desc)
• plunge pool can be further deepened by rocks in the collapse
• waterfall retreats upstream

Question 2

v-shaped valley

Answer 2

• Rivers begin high up in the mountains so they flow quickly downhill eroding the landscape vertically
• Turbulent water results in hydraulic action (desc).
• Abrasion (desc)
• As the river cuts deeper into the valley, the sides are attacked by weathering, as they are exposed to the elements.
• Rocks from weathering fall into the river below due to gravity.
• Fallen rocks further with abrasion in the river which leads to further erosion.
• The river transports the rocks downstream and the channel becomes deeper.

Question 3

meander

Answer 3

• hydraulic action (desc)
• abrasion (desc)
• in a straight river channel, water twists and turns around obstructions such as large boulders
• resulting in areas of slower and faster water movement, as the river starts to become more sinuous
• riffles and pools lead to changes in speed and depths in the river channel
• river flows fastest on the outside bend increasing the erosive power, undercutting to form concave river cliffs, which gradually retreat
• meanders become more pronounced over time

Question 4

oxbow lake

Answer 4

• hydraulic action (desc)
• abrasion (desc)
• in a straight river channel, water twists and turns around obstructions such as large boulders
• resulting in areas of slower and faster water movement, as the river starts to become more sinuous
• riffles and pools lead to changes in speed and depths in the river channel
• river flows fastest on the outside bend increasing the erosive power, undercutting to form concave river cliffs, which gradually retreat
• meanders become more pronounced over time
• the neck of the meander becomes narrower
• deposition seals off the old meander
• over time the abandoned channel may dry up