geography coasts

swash

The movement of water up the beach after a wave breaks.

backwash

Water returning to the ocean from waves washing onto a beach. Moves back down the beach at a 90° angle.

coast

an area of land near the ocean

waves

Wind blows over the sea. Friction with the surface of the water causes ripples to form. These turn into waves.

coastal processes

weathering and mass movement.

destructive waves

strong backwash and weak swash, making a steep beach. This makes erosion greater. High wave in proportion to length.

constructive waves

low wave in proportion to length. Strong swash which deposits material, weak backwash. The beach has a gentler gradient.

fall

freeze thaw weathering shatters rocks from the cliff. The rocks fall to the base of the cliff where they form scree slopes.

flow

fine loose material becomes saturated and flows down slopes.

slide

the top layer of the rock becomes saturated by rain and may slide due to gravity over the layer of rock below.

slump

soft rock cliffs become saturated with rain. This makes them heavy. With undercutting by the sea, they will slump.

weathering

The breaking down of rocks and other materials on the Earth's surface.

biological weathering

when seeds fall into cracks in the cliffs and grow, the roots expand and break away the cliff.

freeze thaw weathering.

When water enters a crack and freezes. This causes the rock to expand.

chemical weathering

weak acids in rain water react with different rock types such as limestone and cause them to break away.

Erosional Processes

the wearing away of land by wave action.

What is hydraulic action

waves force water into the cracks in a cliff.

What happens during hydraulic action

The trapped air expands, causing the cracks to get bigger.

abrasion

materials, like pebbles or sand, grind against a surface, scraping it away like sandpaper.

attrition

sediment carried by the wave knocks into each other. This causes it to get smaller and smoother.

solution

seawater reacts with rocks causing them to dissolve.

wave refraction

causes the energy of the wave to be concentrated on the headland.

headlands

made with more resistant rock and stick out into the sea.

bays

made with less resistant rock and have been eroded back by the sea.

What is a discordant coastline

bands of rock are perpendicular to the sea.

What will you find along a discordant coastline

Different bands of rock.

What is a concordant coastline

bands of rock are parallel to the sea.

What will you find along a concordant coastline

The same bands of rock.

wave cut platform

an area of bedrock visible at the base of some cliffs. It is usually only visible at low tide.

step 1 wave cut platform

cracks or weaknesses in the cliffs are exploited by hydraulic action.

step 2 wave cut platform

weathering weakens the rock at the top of the cliff. Over time, hydraulic action and abrasion erode between the low and high tide forming a wave cut notch.

step 3 wave cut platform

once the wave cut notch is larger and the weathering weakens the top of the cliff, the cliff will collapse and retreat.

step 4 wave cut platform

over time, the cliff will retreat, leaving a rocky wave cut platform that can be seen at low tide.

crack

a weakness in the headland is exploited by hydraulic action.

cave

over time, the crack is eroded by hydraulic action and abrasion. This widens the crack, forming a cave.

arch

Through continued erosion, (HA & A) the erosion eventually breaks through the back of the cave forming an arch.

stack

through erosion and weathering at the top of the arch, the roof collapses because it has weakened, leaving a stack.

stump

continued erosion and weathering of the stack will cause it to reduce in size and topple over into the sea.

sand beaches

flat and wide. Sand particles are small so backwash moves them back down the beach, forming a gentle slope.

shingle beaches

steep and narrow. Shingle particles are large and backwash can't move them back down a beach therefore building up a steep slope.

spit 1

prevailing wind causes long shore drift to occur along the beach, moving sediment.

spit 2

at the end of the beach, sediment will be deposited and grow the beach.

hook

a secondary wind will change the direction of long shore drift and cause the spit to form a hook.

long shore drift

the movement of sediment along the beach waves.

traction

large pebbles rolled across the sea bed.

saltation

bouncing motion of particles which are too heavy to be suspended.

suspension

particles suspended in the water.

solution

dissolved chemicals often derived from limestone or chalk.

bars formation 1

prevailing wind causes longshore drift to occur along the beach.

bars formation 2

deposition occurs at the end of the beach, forming a spit.

bars formation 3

eventually, the spit will grow and join the beach on the other side of the bay forming a bar.

bars lagoon

A lagoon is left in the old bay which will eventually dry out and be filled with sand.

tombolo 1

prevailing wind causes longshore drift to occur along the beach, forming a spit.

tombolo 2

the spit will continue to grow until it reaches the island.

For a sand dune to form it needs:

a large, flat beach, large supply of sand, onshore wind, and an obstacle

sand dune 1

onshore wind transports the sand via saltation and suspension up the beach.

sand dune 2

heavier sand particles settle against an obstacle and lighter particles are transported to settle behind the object.

sand dune 3

sand continues to build up around the obstacle on the windward side, causing the sand dune to grow in size and form a crest.

sand dune 4

height builds up until the structure becomes unstable.

hard engineering

using artificial structures to control natural processes

soft engineering

more natural processes that help adapt and protect the coast.

hard engineering examples

sea wall, gabions, rock armour, groynes

soft engineering examples

beach reprofiling, sand dune regeneration, beach recharge

phase 2 Lyme Regis

2005-2007

cost: £22 mil

positive: promenade encourages tourism

negative: limits access to the beach

phase 1 lyme regis

1990s

cost: £10 mil

positive: very effective

negative: sea wall can make the area look unattractive

phase 3 lyme regis

too expensive

phase 4 lyme regis

2013-2015

cost: £20 mil 💲

positive: homes are protected 🏡

negative: can't find fossils 😱

lyme regis location

South west of the UK, south coast in between Exmouth and Weymouth