Hydrosphere

Question 1

What is the formation of a waterfall (10)

Answer 1

• waterfalls occurs when hard rock sits on top of softer rock (1)
• the softer rock is eroded more quickly- this is known as differential erosion (1)
• this erosion takes place by the process of abrasion, which is when the force of the water throws bedload against the banks causing erosion (2)

-and hydraulic action which is when air is compressed into the river bank causing materials to be dislodged (2)

-the river undercuts the hard rock as the softer rock erodes faster. This can lead to the creation of a plunge pool and a over hang of hard rock (1)

• this is deepened by water swirling around at the base of the waterfall (1)
• the overhang is unsupported so falls down under gravity and it’s own weight (1)
• this causes the waterfall to retreat up stream and creates a narrow steep sided gorge (1)

Question 2

What’s the formation of a V shaped valley 8

Answer 2

-Fast flowing rivers means there is a lot of energy to erode , thus creating vertical erosion

-the river erodes downwards as boulders, stones and rock particles are bounced and scraped along the Chanel bed

-hydraulic action which is when air is compressed into the river bank causing materials to be dislodged (2)

• abrasion is when the force of the water throws bedrock against the banks causing erosion (2)
• as the river cuts down, the steeps sides are attacked by weathering such as freeze thaw weathering, this breaks ups and loosens the rocks and soil and rock

-rocks that fall into the water further assists to erosion

-the loosened material slowly creeps down the slope because of gravity or is washed into the river by rain water

• the end result is a steep sided valley that is the shape of a letter ‘v’ and is a v shaped valley and interlocking spurs

Question 3

What is the formation of an oxbow lake

Answer 3

This happens when meanders become more and more extreme

The river has the most amount of energy on the outside of the river bend. This is where most erosion takes place

-this erosion takes place by the process of abrasion, which is when the force of the water throws bedload against the banks causing erosion (2)

-and hydraulic action which is when air is compressed into the river bank causing materials to be dislodged (2)

Overtime the neck of the meander narrows

• under flood conditions the river will break through the neck of the meander

The water in the meander rapidly loses energy and therefore deposits material. The river flows the fastest in the middle of the channel so deposits at the edge, sealing it off from the river Channel

• the river takes the shorter, straighter path and the old meander is abandoned. It may eventually dry up or fill up with rain water

Question 4

Whats the formation of a meander

Answer 4

-pools and riffles can form in the river as the water twists to move around objects. This can cause the river to swing from side to side

• water flows fastest and has more energy on the outside bend leading to more erosion.

-this can be done from the process of abrasion , which is when the force of the water throws bedload which are carried along in water against the banks causing erosion and scrapes the river bed. (2)

-and hydraulic action which is when the force of the water pushes air into cracks in the bank, blasting them apart. This creates a river cliff

• on the inside of the bend, deposition occurs. This is because the river has a slower current and less energy and therefore can carry its load, it drops t creating a beach.

This can also be assisted by helicoidal flow- this is a corkscrew action where the water moves material from one cliff and deposits it at the next beach

• overtime, continual erosion at the inside and the outside causes the meander to be more extreme