River and Coastal Landforms

Question 1

1.How do interlocking spurs form?

Answer 1

• In the upper course there is more vertical (downward) erosion.
• The river cuts down into the valley.
• If there are areas of hard rock which are harder to erode, the river will bend around it.

Question 2

2.How are meanders formed?

Answer 2

• As the river makes its way to the middle course, it gains more water and therefore more energy.
• The lateral (sideways) erosion on the outside bend due to hydraulic action and abrasion causes undercutting of the bank to form a river cliff.
• Water on the inner bend is slower, causing the water to slow down and deposit the eroded material.
• creating a gentle slope of sand and shingle (this is known as a slip-off slope).

Question 3

3.How are oxbow lakes formed?

Answer 3

• Erosion narrows the neck of the land within the meander and as the process continues
• The meanders move closer together.
• When there is a very high discharge (usually during a flood), the river cuts across the neck, taking a new, straighter and shorter route.
• Deposition will occur to cut off the original meander, leaving a horseshoe-shaped oxbow lake.

Question 4

4.How are waterfalls formed?

Answer 4

• The soft rock is eroded quicker than the hard rock and this creates a step.
• As erosion continues, the hard rock is undercut forming an overhang.
• Abrasion and hydraulic action erode to create a plunge pool.
• Over time this gets bigger, increasing the size of the overhang until the hard rock is no longer supported and it collapses.
• This process continues and the waterfall retreats upstream.
• A steep-sided valley is left where the waterfall once was.
• This is called a gorge.

Question 5

5.How are flood plains formed?

Answer 5

• In the lower course the river is carrying a huge amount of sediment (alluvium).
• When the river floods, excess water spills over the surrounding area.
• During flooding, the velocity of the river is reduced, it loses energy, and deposits sediment, forming the floodplain.
• The floodplain is shaped by the lateral erosion of meanders as they migrate downstream and by deposition of material on the inner bends.

Question 6

6.How are levees formed?

Answer 6

• When a flood occurs, the river loses energy.
• The largest material is deposited first on the sides of the river banks and smaller material further away.
• After many floods, the sediment builds up to increase the height of the river banks and bed.

Question 7

7. How are wave cut platforms formed?

Answer 7

• The sea attacks the base of the cliff between the high and low water mark.
• A wave-cut notch is formed by erosional processes such as abrasion and hydraulic action
  (this is a dent in the cliff usually at the level of high tide).
• As the notch increases in size, the cliff becomes unstable and collapses
  -This leads to the retreat of the cliff face.
• The backwash carries away the eroded material, leaving a wave-cut platform.
• The process repeats.
• The cliff continues to retreat.

Question 8

8.How are headlands and bays formed?

Answer 8

• Formed on Discordant coastlines where more resistant rock such as chalk and limestone take a long time to erode.
• Therefore create the headlands.
• Whereas bays have softer rock such as sand and gravels
• Therefore they erode quicker.

Question 9

9.How are caves, arches, stacks and stumps formed?

Answer 9

• Caves, arches, stacks and stumps are erosional features that are commonly found on a headland.
• Cracks are formed in the headland through the erosional processes of hydraulic action and abrasion.
• As the waves continue to grind away at the crack, it begins to open up to form a cave.
• The cave becomes larger and eventually breaks through the headland to form an arch.
• The base of the arch continually becomes wider through further erosion, until its roof becomes too heavy and collapses into the sea.
• This leaves a stack (an isolated column of rock).
• The stack is undercut at the base until it collapses to form a stump.

Question 10

10.How are rock pools /potholes formed?

Answer 10

• They are formed when sediment and other material carried by a rivers and coasts scour the floor.
• Where exist in the channel floor turbulent flow can cause pebbles to spin around and erode hollows through abrasion.
• As the holes get bigger, even bigger debris can become trapped in the pothole.
• This material further supports erosion.

Question 11

11.How is a beach formed?

Answer 11

• LSD (longshore drift).

- When constructive waves lose their energy the sand and shingle are deposited, normally in sheltered areas such as bays

Question 12

12.Describe the formation of a spit.

Answer 12

• Spits are formed where the prevailing wind blows at an angle to the coastline.
• Sediment is carried by longshore drift and moves along the beach via swash and backwash.
• When there is a change in the shape of the coastline, deposition occurs.

Question 13

13. Describe the formation of a bar.

Answer 13

• A spit can grow across a bay, joining two headlands together.
• This landform is known as a bar.
• They can trap shallow lakes behind the bar, these are known as lagoons.
• Lagoons do not last forever and may be filled up with sediment.

Question 14

14. Describe the formation of a tombolo.

Answer 14

• Longshore drift occurs as waves push sediment (which may consist of sand, silt, and clay) towards the coastline at an angle.
• Instead of landing on the beach, this sediment begins to build up between the beach and an island, creating the bar mentioned above.
• Effectively “tying” the island to the mainland.