Longshore Drift
what is longshore drift?
The movement of sediment along the coastline by waves
what is solution
the transportation of dissolved material in seawater
When does deposition occur?
When waves carrying sediment reach the shore, they will deposit it in areas where they lose energy
what is deposition
the laying down of sediment
Define erosion
Erosion is when the rocks are worn away, in this case by the action of waves.
what does longshore drift do?
it move sediment along the coastline
what does suspension do
it carries fine sediment within the water, the sediment is floating in the water
Name 2 landforms created by deposition
Beaches, spits, bars, tombolos
what does erosion do
it wears away and removes material from the coastline
Name the 4 types of erosion
Hydraulic action, Abrasion, Attrition, Solution
How does longshore drift move sediment?
Swash carries sediment up the beach at an angle, while backwash carries it back down the beach at 90 degreees back into the sea producing a zig zag movement
what are four types of transportation
solution, suspension, saltation and traction
Landform created due to alternating bands of hard and soft rock
Headlands and bays
why does deposition occur when waves lose energy
the waves have less energy to transport sediment , so they drop it as there is not enough energy to carry on carrying them
Define hydraulic action
Waves crash against a cliff and force air into cracks in the rock. The force of this trapped air causes the rock to weaken and eventually break.
A coastline changes direction. What is likely to happen to sediment being transported by longshore drift?
The change in coastline direction can cause sediment to be deposited as the waves lose energy
A river transports large rocks and fine particles towards the sea. Which transportation processes could carry each type of sediment?
Large rocks are transported by traction, smaller rocks by saltation, and very fine particles by suspension. Dissolved minerals can be transported by solution.
Explain the stages in the formation of caves, arches, stacks and stumps
As headlands are unsheltered, they will be assaulted by waves. Any faults or weaknesses in the headland will start to be worn away. Gradually, these faults will deepen until they form a cave. If a cave forms on both sides of the headland, this may break through, forming an arch.
Over time, the arch will get increasingly wide until the roof collapses, leaving a pillar of rock known as a sea stack. This will be eroded and eventually collapse to leave a stump.
A coastline contains both a headland and a bay. Predict where erosion and deposition are most likely to occur and explain why
Erosion is greatest around the headland because wave energy is concentrated there. Deposition is more likely in the bay because wave energy is lower.
This is where sediment being carried by the water wears away the surface, almost like sandpaper.
Abrasion
explain how longshore drift can contribute to the formation of a tombolo
Waves approach the coastline at an angle, causing swash to move sediment up the beach at an angle. Backwash moves sediment back towards the sea at right angles. This creates a zig-zag movement of sediment along the coastline. Continued transportation and deposition can move sediment towards an offshore island until it eventually connects the island to the mainland, forming a tombolo.
Explain how solution, suspension, saltation and traction transport sediment.
Solution transports dissolved material. Suspension carries fine particles within the water. Saltation causes smaller particles to bounce along the seabed. Traction causes larger rocks and boulders to roll along the seabed.
How does geology influence the formation of landforms?
Soft rocks erode faster; hard rocks are slow to erode
Explain how wave refraction affects erosion around headlands and bays
As waves enter shallow water, friction with the seabed slows them down. This causes the waves to bend or refract. Wave energy becomes concentrated around headlands, increasing erosion. Wave energy is lower in bays, meaning there is less erosion and deposition is more likely.
Define Attrition
Rocks crashing into each other result in them becoming smoother and more rounded.