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
what is a tombolo
a ridge of sediment connecting the mainland to an island
what is deposition
the laying down of sediment
what is wave refraction
the bending of wave as they enter shallow water
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
the mainland to an offshore island
what does erosion do
it wears away and removes material from the coastline
what do waves do when they enter shallow water
they slow down and refract or bend
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
what happens when sediment is transported towards an offshore island?
sediment can be deposited aand gruadually builds up towards the mainland
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
why is wave energy different around headlands and bays
refraction concentrates wave energy around headlands and reduces it in bays
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.
A sediment ridge is growing from the mainland towards an offshore island. What conditions would need to continue for a tombolo to form?
Longshore drift must continue supplying sediment, and deposition must continue building the ridge towards the island until it eventually connects with it.
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.
A wave approaches a coastline containing a headland and a bay. Predict how its direction and energy will change as it reaches the coastline
The part of the wave entering shallow water first slows due to friction with the seabed. The wave bends towards the coastline, concentrating energy around the headland and reducing energy in the bay.
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.
Explain the formation of a tombolo from the initial movement of sediment until the island becomes connected to the mainland.
Longshore drift transports sediment along the coastline. Where sediment is deposited, it begins to accumulate. Continued deposition causes the sediment to build towards an offshore island. Eventually, enough sediment accumulates to form a ridge connecting the island to the mainland, creating a tombolo.
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.
Explain how wave refraction and longshore drift can work together to contribute to the formation of a tombolo.
Wave refraction causes waves to bend as they enter shallow water, changing the distribution of wave energy around the coastline. Longshore drift then transports sediment along the coast through the movement of swash and backwash. Continued transportation and deposition can cause sediment to build towards an offshore island. Eventually, the sediment connects the island to the mainland, forming a tombolo.