N5 Coastal landscapes

Explain the formation of a sand bar

Longshore drift transports sand and deposits it in a sheltered area

deposits of sand build up over time until they are above sea level

as the deposits grow into the sea a sand spit is formed

if the spit continues to grow until it joins up with the opposite side of a bay a sand bar is formed.

Formation of a sand spit

Sand spits (long narrow ridges of sand or shingle) form where the coastline changes direction

Longshore drift transports sand and deposits it in a sheltered area. Deposited sand builds up over time until it is above sea level

This deposition continues until the beach extends into the sea to form a spit

Sand spits can also develop a hooked or curved end due to a change in prevailing wind/wave direction.

Mud flats or salt marsh can develop in an area of calm water behind the spit.

Formation of a beach

Formation of a stack

• waves attack a line of weakness, such as a fault line, in the headland

• types of erosion include hydraulic action and corrasion

• continuous erosion will open up the crack and it will develop into a sea cave
  this can happen due to corrasion where stones and pebbles are repeatedly thrown against the cliff face by wave action, wearing it away

• further erosion of the cave, often on opposite sides of the headland, will form an arch

• the base of the arch is attacked by the waves until it eventually collapses

• this leaves behind a freestanding piece of rock called a stack which is separate from the headland.

Formation of a headland and bay

• headlands and bays are found in areas where there are bands of alternating hard and soft rock which meet the coast at right angles for example sandstone a hard rock and clay a soft rock

• headlands and bays are formed by differential erosion

• the softer less resistant rock erodes backwards more quickly forming bays

• when formed the bays then become sheltered by the headlands and erosion slows down

• the harder rock erodes more slowly forming headlands which are left sticking out as rocky outcrops

• the headlands are then vulnerable to erosion as the wave's energy is concentrated here