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Flashcards in Coastal Landscapes Deck (27):
1

Mechanical weathering

The breakdown of rock without changing its chemical composition
ie freeze thaw weathering

2

Chemical weathering

The breakdown of rocks by CHANGING its chemical position
ie carbonation weathering - happens warm and wet conditions

3

Freeze thaw weathering (mechanical weathering)

1) when the temp alternates above 0 degrees

4

Destructive waves

High frequency (10-14 waves/Minute)

They’re high and steep

Strong backwash and weak swash- material is REMOVED from the coast

5

Constructive waves

Gentle low waves and spill unto the beach

Short and wide waves (8-10 waves/minute)

Strong swash and weak backswash- build up the beach

Waves loses energy as it is in friction with the sand

6

Coastal Landforms by erosion

Wave cut platform

Headland and bay

Caves, Arches and Stacks

7

Coastal transportation

Long shore drift

8

Coastal Landforms by deposition

Beaches

Spits

Bars

Sand dunes

9

Example of coastal landforms

DORSET COAST:
Has discordant coastline

Chesil Beach - bar with a lagoon
Durdle Door - an arch
Lulworth Cove - has a bay

10

Types of weathering

Chemical
Physical/mechanical
Biological

11

Headlands and Bays

Occurs on DISCORDANT coastline ( alternating hard and soft rock)

Less resistant rock (soft) is eroded quickly forming a bay which has a gentle slope

Resistant rock is eroded more slowly forming a headland with steep sides

12

Caves, Arches and Stacks

1. Occurs in headlands made of resistant rock
2. Waves crash into the headland and enlarge the cracks (weaknesses) by HYDRAULIC ACTION and ABRASION (define them)
3. Cave is formed by the repeated process
4. An arch is formed when continued erosion deepens the cave until it breaks through the headland
5. A stack is formed when erosion wears away the rock supporting the arch and it collapses
6. A stack is an isolated rock that’s separated from the headland

13

Wavecut platforms

1. More erosion happens at the foot of the cliff ( HYDRAULIC ACTION)
2. Forms a wave cut notch - enlarged as erosion continues
3. Rock above becomes unstable- collapse
4. It’s washed away and a new wave cut notch forms - HYDRAULIC ACTION and ABRASION
5. Cliff retreats - repeated collapses
6. A wave cut platform is the platform that’s left behind

14

What is mass movement

The shifting of rocks AND the lose of material down a slope

It happens when gravity acting on the slop is greater than the form supporting it

15

3 types of mass movement

Slides - material shifts in a STRAIGHT line

Slumps - material shifts with a ROTATION

Rockfalls -

16

Long shore drift

1. The waves follow the direction of prevailing wind
2. They hit the coast at an oblique angle
3. Swash carries material UP the beach IN THE SAME DIRECTION AS THE WAVES
4. The backswash carries material DOWN the beach at right angles
5. Overtime the material ZIG ZAGS along the coast

17

Increase in deposition is caused by what?

1. When there lots of TRANSPORTATION of material into the area

2. When there’s lots of EROSION ELSEWHERE on the coast - lots of material available

18

Formation of a beach

1. Found on coasts between the HIGH WATER MARK and the LOW WATER MARK

2. Constructive waves - it loses its energy when it passes the headland

3. The waves carry the deposited material (sand and shingle)

19

Formation of Spits

1. Form at SHARP BENDS (river mouth)
2. LONGSHORE DRIFT transport sand and shingle past the bend and DEPOSITS it in the SEA
3. STRONG WINDS and WAVES curve the end of the spit
4. Sheltered area behind the spit is protected from waves - growth of SALT MARSH and MUD FLATS (because of deposited material)

20

Bars

EXPLAIN THE FORMATION OF A SPIT FIRST

2: former when a spit joins 2 headlands together
3: it cuts of the bay between the headland from the sea
4: a LAGOON is formed behind the spit

21

Sand Dunes

1. Formed when sand deposited by LONGSHORE drift is MOVED UP the beach BY THE WIND
2) obstacles decrease wind speeds so sand is deposited.
3) the sand is colonised by plants and grasses. Vegetation stabilises the sand and encourages more sand to accumulate there (embryo dunes)
4) overtime the oldest dunes migrate inland as newer dunes are formed. Mature dunes could be 10cm high

22

Sea Wall (hard)

Made of concrete that reflects waves back to the sea

+prevents erosion
+acts as a barrier to prevent flooding

- created a strong backwash (erodes under the wall)
- very expensive to build AND maintain

23

Gabions (hard)

A wall of wired cages filled with rocks. Usually built at the foot of cliffs

+ absorbs wave energy (reduces erosion)
+ cheap and easy to build

- wire cage can corrode over time
- ugly

24

Rock Armour (hard)

Boulders that are piled up along the coast

+ absorbs wave energy (reduces erosion and flooding)
+ cheap

- can be moved around by strong waves (needs to be replaced)

25

Groynes

Wooden/stone fences built at right angles to the coast
They trap material transported by longshore drift

+ create wider beaches (slow the waves-gives greater protection from flooding and erosion)
+ fairly cheap

- starves the beaches further down the coast (makes it narrower)
- narrow beaches don’t protect the coast well (floods and erosion)

26

Beach Nourishment and Reprofiling

Sand/shingle from elsewhere or from lower down the beach that’s added to the upper part of beaches
+ creates wider beaches (slow the waves)
+ gives greater protection from flooding and erosion

- can destroy habitats and kill organisms
- very expensive
-has to be repeated

27

Dune Regeneration

Creating and restoring sand dunes by:
Planting vegetation to stabilise sand
Nourishment

+ provides a barrier between land and sea
+wave energy is absorbed (prevents flooding and erosion)
+ stabilisation is cheap

- protection is limited to a small area
- nourishment is very expensive