As Geography - Coastal Environments - Coastal Processes

Front 1

Weathering

Back 1

The gradual breakdown of rocks.

Front 2

Freeze-thaw weathering

Back 2

Water percolates into cracks in the cliff, then freezes. When water freezes, it expands by about 9% in volume. This exerts pressure, causing the cracks to widen and eventually break away to collect at the base of the cliff as scree.

Front 3

Salt weathering

Back 3

When salt water evaporates, it leaves behind salt crystals. These grow larger over time and exert stresses in the rock, causing it o break apart.

Front 4

Wetting and drying

Back 4

Clay rich rocks (e.g. shale) expand when they get wet and contract when they dry out, causing them to crack.

Front 5

Carbonation

Back 5

The slow dissolving of calcium carbonate from rocks such as limestone and chalk. When it absorbs carbon dioxide from the air, water forms a weak carbonic acid which then reacts with calcium carbonate in certain rocks to form calcium bicarbonate, which is easily dissolved.

Front 6

Biological weathering

Back 6

Can include plants growing in small cracks and the roots prising apart rocks. Also, birds and animals dig burrows in cliffs.

Front 7

Mass movement

Back 7

The downhill movement of rock and soil in response to the force of gravity. It is quite common at coasts because of the constant undercutting of the cliffs by the sea, making them unstable and prone to collapse.

Front 8

Landslide

Back 8

Rapid movement of detached slabs of rock down a slide plane.

Front 9

Rockfall

Back 9

Individual rock fragments fall off a cliff face, often due to freeze-thaw.

Front 10

Mudflow

Back 10

Saturated soil flows downhill, often triggered by heavy rain.

Front 11

Rotational slip

Back 11

Common coastal landslips in weak rocks, e.g. sands and clays.

Front 12

Soil creep

Back 12

Very slow downhill movement of individual rock particles.

Front 13

Hydraulic action

Back 13

The force of the water can carry out a lot of erosion. When air is blasted into cracks (cavitation), loose rocks are dislodged and removed. Gradually, a wave-cut notch forms, undercutting the cliff and eventually leading to cliff collapse and retreat.

Front 14

Corrasion

Back 14

Rocks caught up in surging seawater are hurled at a cliff face, causing it to be eroded.

Front 15

Abrasion

Back 15

The sandpapering effect of loose rocks being scraped across bare rock.

Front 16

Attrition

Back 16

When rocks carried by seawater bash against each other.

Front 17

Traction

Back 17

The rolling of large and heavy rocks along the seabed.

Front 18

Saltation

Back 18

The bouncing of slightly smaller rocks along the seabed.

Front 19

Suspension

Back 19

When sediment is held in the water.

Front 20

Solution

Back 20

When sediment dissolves completely.

Front 21

Deposition

Back 21

Occurs in low-energy environments, e.g. bays and estuaries. When sand is deposited on a beach, it can be transported further inland by the wind to form sand dunes.