Coastal Erosion

Question 1

What is coastal erosion?

Answer 1

The wearing away of a material through abrasion, attraction, solution and hydraulic action and the removal of the material by water, wind or ice.

Question 2

What is weathering?

Answer 2

Weathering is the disintegration and decomposition of rocks in situ (it is not removed) by the combined actions of weather, animals and plants

Question 3

Sub-Aerial processes

Answer 3

Land based and occur above the waterline. Include mass movement and weathering

Question 4

Mass movement

Answer 4

Downhill movement of cliff material under influence of gravity.

Question 5

Marine processes

Answer 5

Processes associated with action of waves including transportation, deposition (depositing of sediment, sand, pebbles by constructive wave action) and erosion.

Question 6

Types of weathering (3)

Answer 6

Physical - temp, water, wind

Chemical - acidic rainwater reacting with mineral in rock

biological - living organisms breaking rock

Question 7

Rockfall

Answer 7

Occurs in hard rock cliffs. Fragments of rock break away due to weathering (eg. Freeze-thaw)

Question 8

Rotational slumping

Answer 8

Rainwater penetrates permeable layer (gravel) and weighs down impermeable layer of hard rock leading. Cliff slides down in layers due to weight on hard rock

Question 9

Hydraulic action

Answer 9

Waves hit base of cliff :> air compressed in cracks, joints, folds in rocks. Explosive action as waves retreat. Can break off cliffs in huge chunks

Question 10

Abrasion

Answer 10

Sandpaper effect. Caused by sediment carried by waves between low and high watermarks. Can impact base of cliff or headland

Question 11

Attrition

Answer 11

Rocks bump/ bang each other in turbulent waters breaking into smaller chunks

Question 12

Solution

Answer 12

Calcium based rocks (ie limestone)are dissolved by chemicals in seawater.

Question 13

Caves, arches, stacks and stumps

Answer 13

Cracks cause caves through hydraulic action and abrasion.
Two caves align on either side of headland… break, collapse to crest arch.
Weathering and gravity (mass movement) cause arch to collapse = stack
Stack erodes away to stump

Question 14

Headland creation

Answer 14

Soft rock on either side of hard rock. Erodes away. Previous rock eroded away forms beach through deposition

Question 15

Ocean waves

Answer 15

Wind friction against water causes waves to be made in circular motion. as approaching shore friction on seabed causes slowing down of wave and crest to move forward and fall

Question 16

Swash

Answer 16

Rush of seawater up beach after wavebreak

Question 17

Backwash

Answer 17

Swash running back down beach due to gravity.

Question 18

Constructive wave

Answer 18

Swash > backwash ….. builds the beach due to sediment
Weaker than destructive
Creates wide flat beaches
Lower wave height but greater wavelength (ie more infrequent waves)

Question 19

Destructive waves

Answer 19

Backwash > Swash …. Tall and powerful and erode coastline. Crash onto beach and drag material away. Power driven by gravity due to large wave height and short wavelength (higher wave frequency)
Steep beaches

Question 20

Wind speed and waves

Answer 20

Wind faster than wave …. Energy transferred to wave and more destructive wave
Duration wind …. Longer wind blows then more time to transfer energy and build waves

Question 21

The fetch

Answer 21

Distance traveled over open water before hitting coastline. Longer fetch = larger wave

Question 22

Longshore drift

Answer 22

Movement of sediment along beach. Wave approaches shore from angle (ie 45 degrees) and backwash is perpendicular to beach.

Question 23

Spit

Answer 23

A spit is a long narrow beach made from sand or shingle that is joined to the mainland but stretches out into the sea

Caused by deposition and Longshore drift.

Area is shallow and calm

Question 24

Hard engineering

Answer 24

Man made structures to manage coastline
Groynes - wood rock that stop movement of sediment along beaches
Sea wall - curved concrete walls to reflect wave energy
Rock armour - boulders and rocks that weaken way energy by getting in way
Gabions - like rock armour but smaller rocks and encased in cages

Question 25

Soft engineering

Answer 25

Technique working with nature to protect coast

Managed retreat - let sea erode as nature intends and allows flooding
Beach nourishment - add sand to beaches to increase size - absorbs wave energy

Question 26

What is mass movement?

Answer 26

Is the downhill movement of cliff material under the influence of gravity. Rotational slumping and rock fall are both types of mass movement.