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Flashcards in Coasts Deck (40)
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1

Name the processes that happen at the coast

- Weathering
- Transportation
- Erosion

2

What is Mechanical weathering

The breakdown of rock at without changing it chemical composition

3

Process of Mechanical weathering

1. Water fills a crack or joint
2. Water freezes -> crack is widened (pressure)
3. Repeated FREEZE-THAW-ACTION increases the size of the rock
4. Block of rock falls off, loose blocks are called scree

4

What is Chemical weathering

The breakdown of rock by changing its chemical composition
- Warm wet conditions

5

Process of Chemical weathering

1. Rainwater has co2 dissolved in it -> weak carbonic acid
2. Reacts with rock that contains calcium carbonate, wears away the rock

6

Process of Biological weathering

1. Roots of vegetation grow in cracks
2. Splits the rock apart
3. Organic acids released speed up chemical weathering

7

What is mass movement

When material shifts/ moves down a slope/ surface

8

Sliding (mass movement)

Large chunks of rock slide down the slope QUICKLY without warning

9

Slumping (mass movement)

(Clay cliffs)
Clay becomes saturated, during heavy rainfall and OOZES down towards the sea

10

4 Processes of erosion

- Hydraulic action
- Abrasion
- Attrition
- Solution

11

Hydraulic action

1. Water is force into cracks in the rock
2. Compresses air
3. Wave retreats -> air blasts out
4. Rock breaks apart

12

Abrasion

- Eroded particles in the water SCRAPE and RUB against the rock, removing small pieces

13

Attrition

- Sediment collides with each other and breaks into smaller pieces.
- Their edges get rounded off

14

Solution

- Weak carbonic acid in seawater dissolves material from the rock, like chalk and limestone

15

Which waves carry erosive power

DESTRUCTIVE waves

16

Formation of a wave cut notch/platform

- Sea erodes the base of a cliff
- The notch increases in size -> cliff collapses, rock above is unsupported
- Collapsed material is carried by backwash
- New wave cut notch starts to form
- Repeated collapsing results in the cliff retreating

17

Formation of a headland and bay

- Alternating bands of hard + soft rock make up the coast line
- Destructive waves -> erode the soft rock to from bays
- More resistant rock sticks out as a headland (steep sides)
- Bay -> Constructive waves deposit + build up beaches

18

Formation of a cave, arch and stack

- Waves crash into the headlands + enlarge cracks (HA or ABRASION)
- Repeated erosion causes a cave
- Cave deepens until it breaks through the headland - forming an arch
- Rock supporting arch wears away - collapses
- Forming a stack

19

4 Processes of transportation

- Traction
- Saltation
- Suspension
- Solution

20

Traction

LARGE pebbles are PUSHED along the sea bed by water

21

Saltation

PEBBLE sized particles are BOUNCED along the sea bed by water

22

Suspension

SMALL particles are CARRIED along the water

23

Solution

SOLUBLE material dissolve in the water and are CARRIED along

24

Process of Long shore drift

- Waves follow the direction of the prevailing wind
1. Waves break on to the beach (swash)
2. Particles of sediment are carried with waves
3. Backwash carries material DOWN the beach, at right angles
4. Process repeats along the beach (zigzag)

25

What is deposition

Material carried by the sea water is DROPPED on the coast

Greater deposition than erosion -> Coast is built up

26

Formation of a spit

1. Longshore drift occurs along the coastline
2. Coastline ends -> material is deposited (cant go any further, change in depth)
3. Material builds -> ridge of shingle and sand
4. Strong winds -> Curve the end around
5.

27

Formation of a beach bar

1. Constructive waves approach in the PVD
2. Sediment is moved up the beach is swash
3. Some is deposited, rest moves in backwash
4. Some sand will be deposited in the bay between 2 headlands, rest is across forming a beach bar
5. A lagoon is formed behind, where the bay was

28

Properties of DESTRUCTIVE waves

- Strong BACKWASH
- ERODE sand FROM the beach
- More frequent than constructive
- Sand is deposited out at sea -> causing an OFFSHORE BAR

29

Properties of CONSTRUCTIVE waves

- Strong SWASH
- Transports sand UP the beach
- Less frequent than destructive
- Sand is deposited as a BANK or BEACH BERM

30

When does deposition occur

When a wave LOOSES ENERGY and can no longer carry the sediment load