Deposition
Geography: Cambridge International GCSE (2027 Exams), topic 2.1.4
Coastal Deposition
Coastal deposition describes the sea dropping sediment (or material) being carried by the water at the coastline. Coasts grow in size when more sediment is deposited on the coast than is lost to the process of erosion.
Why does deposition happen?
- Deposition happens when constructive waves break on the shore. The sediment being carried by the sea is put (deposited) on the coastline.
- This usually creates beaches made of sand or shingle in the area between the 'high' water mark and the 'low' water mark.
- The high water mark is the point the highest up the beach that the sea level rises to.
- The low water mark is the point the lowest down the beach that the sea level falls to.
Water marks
- An image of high and low water marks.
What increases the amount of deposition?
- If erosion on the nearby coast is high, then lots of rock and sand will fall into the ocean. This will increase deposition on nearby beaches.
- The more sediment in the ocean, the more deposition there will be.
Why are some beaches sandy & some shingle?
- Sandy beaches are created by sand being deposited on the shoreline.
- Sandy beaches are usually very long, wide, and flat because particles of sand are very small and easy to wash back into the ocean with the backwash.
- Shingle beaches are made when pebbles and shingle are deposited on the coast. Shingle and pebbles are big and hard to wash back into the ocean, so they build up (making short and steep beaches).
Test yourself on Deposition
What type of waves cause coastal deposition?
What increases the amount of coastal deposition taking place?
What do we call the dropping of material in seawater onto the coast?