Geography: Coastal Erosion

Weathering

The breakdown or deterioration of rocks into smaller pieces in one place

Erosion

The wearing away of rocks by water, wind or ice

Mountainous coastline

A coastline where the mountains extend to the sea

Glaciated coastline

A coastline dominated by ice

Reef coastline

A coastline dominated by coral

Coastal plain coastline

A flat stretch of land near the sea

Delta coastline

Formed at the mouth of a river when the river meets a body of water with low velocity

Step one of wave formation

The prevailing wind results in parts of the water depressing and raising due to friction. Risen water is pushed by more wind.

Step two of wave formation

Prevailing wind creates friction with ocean. Parts will depress and rise.

Step three of wave formation

Waves move in a circular fashion in a deep ocean

Step four of wave formation

As waves approach the shore, friction slows the base down

Step five of wave formation

Friction with the seabed causes the waves to move in an elliptical fashion. Wave length shortens due to friction

Step six of wave formation

Wave slows, top wave continues at same speed and breaks

Fetch

The distance a wave travels

High wave energy

Destructive

Low wave energy

Constructive

Tall and narrow wave

Destructive

Wide and shallow wave

Constructive

Strong backwash

Destructive

Weak backwash

Constructive

Strong swash

Constructive

Weak swash

Destructive

6-8 of these waves per minute

Constructive

10-14 of these waves per minute

Constructive

Less than 1m tall

Constructive

Abrasion

Caused by large waves hurling beach material at a cliff

Solution

Salt water or other acids cause rocks and cliffs to slowly dissolve

Attrition

When waves cause rocks and boulders to bump into each other, causing parts to chip off until they break up into small particles

Hydraulic action

The force of waves compresses air into cracks and causes rocks to break apart

Headlands and bays

Alternating areas of hard rock jutting out into the sea and soft rock that has been weathered/eroded back

Caves, arches, stacks and stumps

Landforms caused by erosion

Wave cut platform formation step one

Erosion at the base of the cliff at high tide creates a notch

Wave cut platform formation step two

Over time the notch is enlarged by attrition and hydraulic action

Wave cut platform formation step three

The notch makes the cliff unstable and gravity collapses it over time

Wave cut platform formation step four

The process repeats and the cliff retreats inland

Wave cut platform

The base remains of a cliff that has been eroded away

Step one of formation of caves, arches, stacks and stumps

A fault opens in the rock

Step two of formation of caves, arches, stacks and stumps

Due to hydraulic action, the fault become bigger and forms a notch

Step three of formation of caves, arches, stacks and stumps

Abrasion and hydraulic action widens the notch into a cave that keeps getting bigger

Step four of formation of caves, arches, stacks and stumps

Due to waves and erosion, the back of the cave opens, leaving an arch

Step five of formation of caves, arches, stacks and stumps

The arch keeps widening until the roof becomes too heavy and it collapses under its own weight, forming a stack: standing but still undercut

Step six of formation of caves, arches, stacks and stumps

The stack eventually collapses, leaving a stump

Longshore drift

The transportation of materials along the coastline

Step 1 of longshore drift process

The prevailing wind causes the tide to come in at the beach at an angle

Step 2 of longshore drift formation

The swash goes further up the beach due to the angle of the tide, bringing and depositing beach material with it

Step 3 of longshore drift formation

The backwash drags the beach material back at right angles to the beach

Step four of longshore drift formation

The process repeats until a spit forms

Spit

A landmass formed when deposited beach material accumulates

Salt marsh

If the tide curves, a salt marsh will form behind the spit

Deposition

A wave with low energy (due to low wind) drops any pebbles and shells it may have been carrying