Coastal landforms

What is swash?

When waves wash up onto a shoreline, transferring energy up the beach

What is backwash?

When waves retreat down a beach & into the sea, pulling away sediment

What is fetch?

When wind blows over a sea or lake, generating waves

Longer fetch = more powerful waves

What are constructive waves?

Waves that build up beaches due to their swash being stronger than their backwash

The waves are low & have little energy

What are deconstructive waves?

Waves that destroy beaches due to their backwash being stronger than their swash

The waves gain height as they approach the beach & have lots of energy

What is longshore drift?

When sediment is transported along a coastline

This happens in a zig-zag movement where swash carries sediment up the beach at an angle (dictated by the prevailing wind) & backwash carries sediment back down the beach 90° to the coastline

How are headlands & bays formed?

When coastlines have bands of soft & hard rock perpendicular to the sea, headlands & bays are formed

This is because differential erosion causes the bands of soft rock to erode faster (forming bays) & the bands of hard rock are left sticking out (forming headlands)

Overtime, the headlands will erode & make the coastline straight; then the process will start again

How are beaches formed?

When waves lose energy & therefore deposit the material they are transporting

What are the differences between sandy beaches & shingle beaches?

Sandy → wide, gently sloping beach profile, formed in low energy areas where constructive waves dominate (e.g. bays), often backed by sand dunes

Shingle → narrow, steeply sloping beach profile, formed in high energy areas where deconstructive waves dominate, often backed by cliffs

How are spits formed?

Sediment is carried by longshore drift along a coastline

When the coastline changes direction, the sediment is deposited into the sea

Overtime, the sediment builds up above sea-level, forming a spit (spits can develop a hooked end when the wind changes direction)

The area behind a spit is very sheltered & so salt marshes or mud flats often form due to the deposition of silt

How are bars formed?

When spits grow across a bay & join 2 headlands together

Shallow lakes can get trapped behind the bar - these are lagoons (lagoons do not last forever as they can get filled up with sediment)

How are caves, arches, stacks & stumps formed?

Hydraulic action & abrasion erode headlands, creating cracks & notches which open up into a cave

The cave becomes larger due to further erosion & eventually breaks through the headland to form an arch

The base of the arch widens overtime until it is too unstable to hold the headland above it, causing it to collapse into the sea & leave behind a stack

Waves attack the base of the stack, causing it to weaken & fall, leaving a stump