Geography Chapter 10: The Sea

Waves

Waves are formed by wind blowing over the sea surface.

the fetch

The distance a wave travels before reaching land

The longer the fetch...

the stronger the wave

the swash

the water that rushes up the beach when a wave breaks

the backwash

the water that returns back down the beach after the swash

Constructive waves

Waves in which the swash is greater than the backwash.

Destructive waves

Waves in which the backwash is greater than the swash.

Hydraulic Action

The physical force of the waves breaks material off the coastline.

Abrasion

Loose material is thrown against the coastline by waves and this action breaks more material off the coastline.

Compression (Compressed Air)

When waves crash against a cliff, air gets trapped in the cracks on the cliff face and becomes compressed. When the waves retreat, the pressure is suddenly released, and this creates a mini shockwave. This compression and release happens repeatedly until the rock eventually shatters.

Solution

Some rocks, such as limestone and chalk, are dissolved by acids in the sea water.

Attrition

The stones that are carried in the waves are constantly hitting against each other. Over time, they become smooth and rounded. This can eventually lead to the formation of sand.

A bay

a curved opening into the coastline where waves have eroded softer rock.

A headland

a narrow finger of rock sticking out into the sea

bays and headlands formation

waves crash against coastline, soft rock erodes faster than hard rock, hydraulic action wears away and breaks off bits of the softer rock, the sea uses the stones it carries to hit off and wear down the coastline, water fills in the place where the soft rock used to be to form a bay, the harder rock remains resistant to erosion and stands out on either side of the bay to form headlands

example of bay

bantry bay

example of headland

missen head

A sea cliff

a vertical or steep slope on the coastline

a sea cave

a tunnel at the base of a cliff

A sea arch

an arch-shaped tunnel that stretches through a headland

A sea stack

a pillar of rock cut off from the cliff or headland and left standing on its own

A blowhole

a passage that links the surface of the cliff top with the roof of a sea cave.

longshore drift

when the sea transports sand and sediment in a zig-zag pattern down along the shore

A beach

a build-up of sand and shingle that has been deposited by constructive waves between the high-water and low-water mark

beach formation

the swash carries material up the shore and deposits it, the waves are unable to carry all the material back because the back wash is weaker than the swash, the heaviest material is dropped first, at the top of the beach and the finer material is carried back down, closer to the shoreline, over time, this material builds up

beach example

Rosslare in Co. Wexford

A sand spit

a long ridge of sand or shingle that stretches across a bay and is connected to one side of the bay

A lagoon

an area of water that has been cut off from the sea by a sandbar

A tombolo

a ridge of sand that connects the mainland to an island

3 ways that people use the sea

food supply, recreation, transport

what is a sea wall

a wall that breaks the power of incoming waves, their curved tops push waves back out to sea

what is rock armour

large boulders at the bottom of a cliff or in front of a sand dune

what are groynes

concrete or wooden structures built at right angles to the coastline

what are gabions

wire cages filled with small stones