Geo Coastal Environments

What are the 2 coastal processes

marine processes (water-based), terrestrial processes (land-based)

what does wave action do

erode transport and deposit material

how is wave action formed

formed by winds blowing over the surface of the sea

movement of water up the beach

swash

return movement

backwash

what are the 2 waves

constructive and destructive waves

characteristics of constructive waves

strong swash, weak backwash, long wavelength, low wave height, low freq, gently sloping beaches

characteristics of destructive waves

strong swash, weak backwash, short wavelength, short wave height, high wave height, high freq, steep beaches

erosion

destructive waves erode the coastline

4 types of erosion

hydraulic action, attrition, abrasion, corro

hydraulic action

force of the waves hitting the coast

attrition

material carried in the waves bumps against each other which causes them to break down into smaller, smoother pieces. (forming sand and shingle)

corrosion

seawater is slightly acidic and gradually dissolves some types of coastal rock

abrasion

when waves pick up material and hurl it at the coast

transportation

the movement of eroded materials along the coastline by waves, currents, and tides.

4 types of transportation

traction, saltation, suspension, solution

traction

large heavy material is dragged along the sea floor

saltation

smaller material bounces along the sea floor

suspension

the fine material held in water

solution

dissolved material carried in the water

what is deposition

laying down of sediment carried by water

describe longshore drift (main process of weathering and deposition)

1. prevailing wind pushes the waves at an angle to the beach

2. waves break

3. swash carries material up the beach at the same angle

4. backwash carries material down at a 90 degrees due to gravity

   transporting material along the beach in a zig zag movement

what is long shore drift

movement of material along the shore by wave action

what is weathering

the breakdown of rock in it’s original place

what are the 3 types of sub-aerial weathering

mechanical, chemical and biological

mechanical weathering

freeze-thraw of frost-shattering - water freezes and expands, crack grow

salt evapouration - water evaporates, salt crystals, salt expands, crack grow

chemical weathering

slightly acidic rainwater reacts with mineral in rock → creates new material

biological

plants grow inside cracks → push cracks open

tiny organisms → produce chemicals that break down surface layer of rock

burrowing animals destabilise ground → increase pressure on cracks

what is mass movement

the downhill movement of material under the influence of gravity

slide

blocks of rock slide down hill

slump

saturated soil slumps along a curved surface

fall

fragments of rock break away from the cliff face

flow

saturated soil flows down a slope

where do headlands form

on alternating bands of resistant and less resistant rocks running perpendicular to oncoming waves (discordant coastline)

how is a bay formed

less resistant rock is eroded back

what is a wave cut platform

gently sloped surface found at the foot of a cliff

how is a wave cut platform formed

sea attacks base

wave cut notch is formed

undercutting

leads to instability and collapse

how is a stump formed

cracks in headland

exploited by erosional processes

crack widen forming cave

larger and breaks through the headland

arch formed

base of arch becomes thinner and wider

roof of arch collapses

stack formed

stack is undercut at base

stump formed

types of depositional landforms

beach, spit, sandbar, lagoon, barrier island

beach

Deposition through constructive wave movement

spit

extended stretch of sand extends out to sea from the shore

how is a spit formed

Sediment transported by longshore drift

Where coastline changes direction

shallow, sheltered area allows for deposition of sediment

increased friction, more deposition occurs 

a spit slowly builds up to sea level and extends in length

wind changes direction, wave pattern alters, hooked end

sandbar

spit forms and joins two headlands together

lagoon

formed behind tombolo or bar - small body of water cut off from sea

barrier islands

form parallel to coast - bar joins two headlands - open at one or both ends

tombolo

spit connects to an island

2 types of rock

hardrock and softrock

hard rock characteristics

high, steep cliffs

soft rock characteristics

lower and gentle cliffs