Characteristics and formation of landforms resulting from deposition
For the exam, you will need to know about the characteristics and formation of the following landforms resulting from deposition: 1. Beaches 2. Spits 3. Bars
1. Beaches
A beach is the zone of deposited material that extends from the low water line to the limit of storm waves. The beach or shore can be divided in the foreshore and the backshore.
What do beaches look like on a map?
How are beaches formed?
Beaches are accumulations of sand and shingle (pebbles) found where deposition occurs at the coast.
Sandy beaches are often found in sheltered bays, where they are called bay head beaches. When waves enter these bays, they tend to mirror the shape of the coast. This is called wave refraction. This happens because waves enter shallower water. Wave refraction causes the waves to spread out and reduce the wave energy in the bay, which is why deposition happens here.
Beaches have different characteristics: Some are straight and others in bays are likely to be curved. The material found on a beach (i.e. sand or shingle) depends on the geology of the area and wave energy.
Gently sloping beaches form due to strong destructive waves that backwash more material away from the beach than they swash up the beach.
Steeply sloping beaches are formed by constructive waves that swash more material up the beach than they backwash away, building up a steep beach gradient.
2. Spits
A spit is a depositional landform formed when a finger of sediment extends from the shore out to sea, often at a river mouth. It usually has a curved end because of opposing winds and currents.
What do spits look like on a map?
How do spits form?
A spit is a narrow finger of sand and shingle jutting out into the sea from the land.
As sediment is transported along the coast by longshore drift, it becomes deposited at a point where the coastline changes direction or where a river mouth occurs.
As more and more sediment is deposited, the feature extends into the sea.
Away from the coast, the end of the spit is often affected by the wind direction and the waves approaching from different directions and the spit becomes curved.
Over time, the sediment builds up to form new land and a spit is formed.
It soon becomes colonised by plants.
On the landward sheltered side of the spit where water is calm, mudflats and salt marshes form.
Occasionally longshore drift may cause a spit to grow right across a bay, trapping a freshwater lake or lagoon behind it. This feature is called a bar. An example can be seen at Slapton Ley in Devon or Chesil Beach in Dorset.