Coastal Landscapes and Processes- PART 1

mechanical weathering example:

freeze thaw- water gets into rock cracks, temp drops below 0, water expands and turns into ice, pressure on rock, fragments

the chemical weathering example:

acid rain- weak acids in rain, carbonates in limestone are dissolved, rock breaks or disintegrates

biological weathering example:

plants and animal on land-

eg seeds fall into rock cracks, grow, roots add pressure, rock breaks

eg burrowing animals like rabbits tunnel through soil layers, break rock

mass movement definition

when large amount of material moves downwards due to gravity

examples of mass movement

1. slumping

2. mudflow- saturated soil and weak rock flows down a slope

3. landslide- blocks of rock slide downhill

4. rockfall- fragments of rock break away from cliff face often due to freeze thaw weathering

slumping definition

rapid mass movement which involves a whole segment of cliff moving down slope in a rotational manner

mudflow definition

after heavy rain, material becomes saturated + extra weight causes material to become unstable and flow down slope

erosion definition

wearing away of rock over time

attrition definition

sand and pebbles carried by waves are thrown against cliff, eroding cliff and breaking off rock

hydraulic action definition

pressure and force of water crashing against cliff, eroding coastline

solution definition

rock such as limestone and chalk dissolve in sea water due to salt and other acids in seawater

abrasion definition

sandpaper effect- rocks rub against each other, causing friction, wearing away rock

state the 4 ways that the sea transports and deposits material along the coast

traction- large sediment eg pebbles roll along the sea bed

solution- minerals dissolve in seawater and are carries in solution, usually near chalk and limestone cliffs

suspension- small particles such as sand and clay are carries in water

saltation- small pieces of shingle or large sand grains bounce along sea bed

transportation definition

movement of eroded material

deposition definition

material transported by seawater is dropped by constructive waves

longshore drift definition

zig zag movement of material along the shore by wave action driven by the prevailing wind

• wave approach beach at and angle

• swash carries material up and along beach

• backwash carries material back down beach at right angles due to gravity

what 5 factors increase deposition

1. water loses energy

2. too much sediment being carried

3. little or no wind

4. sheltered area eg bay

5. shallow water

define constructive waves

waves that deposit more material than they erode

define destructive waves

waves that take away more material than they deposit

what rock type are bays made from

• less resistant rock

• soft rock

• eg clay

• eroded more quickly

• sheltered by headland which reduces erosion and increases deposition

what rock type are headland made from

• hard rock

• more resistant

• eg chalk or granite

• eroded more slowly

• protrudes into sea, exposed to full force of waves, more vulnerable to erosion

what factors affect the landforms formed

1. rock type- hard/soft rock

2. geological structure- concordant/ discordant coastlines, joints and faults

3. wave action- destructive and constructive waves

effects of rock structure on erosion- joints and faults

• rocks that are well jointed or have many faults erode more quickly, less resistant- waves exploit lines of weakness

• rocks with few joints are more resistant to erosion

geology and characteristics of concordant coastlines

• layers of alternating rock

• rock type is all the same at front of coastline, so erosion is fairly even

• no bays, just headlands

• hard rock such as chalk and limestone

• waves direction is parallel to coastline

name an example of a concordant coastline

Durlston Head

geology and characteristics of discordant coastlines

• consist of alternating bands of hard and soft rock

• wave direction is 90 degree to coastline

• hard rock eg Ballard Point

• soft rock eg Studland Bay, Swanage Bay

• soft rock is eroded much faster forming bays

• hard rock eroded slower, forming headlands

characteristics of constructive waves

• strong swash and weak backwash- deposits more sediment than is taken away, builds beach

• usually found on gently sloping beaches

• break infrequently- 8-10 times a min

• long in relation to height

characteristics of destructive waves

• strong backwash and weak swash- takes away more sediment than it deposits

• found on steep beaches

• high in relation to length

• break frequently- 10-14 times a min

what is the fetch

the length of water over which the wind has blown

• the greater the fetch, the stronger the wind, the more powerful the wave, more erosion

what factors affect the size of a wave

• speed of wind

• fetch

• wind strength

the higher the wind speed…

the more destructive a wave is

name 2 factors that affect the rate of coastal erosion

weather

climate

what weathering occurs on cliffs in the winter

freeze thaw

which direction does the prevailing wind in the UK come from

south west

the coastlines of devon and cornwall experience winds that have blown several thousand km across…

Atlantic Ocean

• means longer fetch, stronger wind, more powerful wave faster rate of erosion

how do the UK’s weather and climate affect rates of coastal erosion

seasonality- winter= higher rate of erosion- more storms, more freeze thaw weathering, more powerful waves

intense rainfall= saturated cliffs= more mass movement

mild temperatures= more salt weathering

spring lower rates of erosion