River landforms

Question 1

Waterfall

Answer 1

• Alternating bands of hard rock and soft rock
• The soft rock is ontop of the hard rock is eroded faster
• There is now an overhang of hard rock which collapses quickly due to gravity and hydraulic action (the force of the water forces air into the rocks causing them to expand so they break down)
• Attrition (rocks bash into each other making them smaller and rounder) takes place in the plunge pool
• Which is made deeper by abrasion (rocks scraping along the river bed and banks breaking them down)

Question 2

What is a Gorge formed by?

Answer 2

The constant retreating of a waterfall upstream

Question 3

Rapids

Answer 3

• Alternating bands of hard rock and soft rock on a river bed
• The soft rock erodes faster than the hard rock due to hydraulic action (the force of the water forces air into the rocks causing them to expand so they break down) and abrasion (rocks scraping along the river bed and banks breaking them down)
• This causes the river bed to be uneven
• Which results in a turbulent river flow which is what often causes the water in the river to be white
• Hard rocks protrude out of the river

Question 4

Interlocking spurs

Answer 4

• The river is very shallow and narrow in the upper course
• Big boulders cause the river to have a turbulent flow and because of the turbulent flow a lot of energy is wasted
• River lacks energy to break through the end of the valley
• The lack of erosion creates a v shape so the bottom of the valley appears to be interlocked
• Land has hard rock and soft rock
• the river winds its way around the more resistant rock and cuts down into the soft rock leaving interlocking spurs

Question 5

v shaped valley

Answer 5

• In the upper course of the river it has a very small discharge as most of the energy is being used to overcome friction and erode vertically due to hydraulic action (the force of the water forces air into the rocks causing them to expand so they break down) and abrasion (rocks scraping along the river bed and banks breaking them down)
• this leaves the sides of the river channel to be steep and unsupported
• the sides are also weakened by mass movement (large scale movement of rock) and weathering (natural process that causes the break down of rocks) causing bits of rock to slip down the channel to be washed away by the river.
• This causes a v shape

Question 6

floodplains and levees

Answer 6

• when the river is not in a flood the floodplains are flat on either side of the channel
• In a flood, large boulders are carried by the process of traction and then are deposited first on the river banks. However lighter sediment is carried further by saltation (smaller rocks are bounced along the river bed) and suspension (fine particles are carried along in the river flow) then deposited which is called SEQUENTIAL DEPOSITION
• Floodwaters recede over time, leaving deposited material on the flood plains making them wider and deeper
• The boulders deposited on the banks form levees

LATERAL EROSIÓN OF RIVERS MAKES FLOODPLAIN WIDER