Transport Process Landforms Flashcards
How are beaches formed?
Beach sediment is deposited mainly by constructive waves, and the breaking action of these waves may form beach cusps/berms.]
Longshore drift may also bring beach material from erosional sources, which is deposited by waves as they move material along the beach.
Destructive waves shape a beach by creating storm ridges at the backshore during high tide. Backwash also scours sediment away from the beach.
How are offshore bars formed?
A long ridge of sand/pebbles formed a short distance out to sea, in shallow water where destructive waves breaks before reaching the beach.
These waves scour the seabed and throw materials forward into a heap. Currents in the sea also supply sediments.
How is a barrier beach formed?
This is a beach that connects 2 areas of land, with a lagoon forming behind.
They form with a plentiful supply of sand/shingle, shallow nearshore/offshore areas, waves with enough energy to move the sand/shingle, and rising sea level to push the sediment towards the shore.
How are nearshore bars formed?
They are smaller versions of barrier beaches. They commonly form in the surf zone where storm waves break, scooping up the sediment and adding them to onshore transport to pile them up in a long ridge, parallel to the coast. Bars may be sinuous and attached to the shore in some places.
How are tombolos formed?
Formed after longshore drift carries sediment across a gap between the mainland and an island, forming a narrow low ridge of sand and pebbles.
How is a spit formed?
When there is a dominant longshore drift direction, pleanty of sediments from mass movement/erosion and a gap in the coastline (estuary/bay).
Sediments are transported by sediment along the coast. When they reach the gap in coastline, they are carried a short way in the same direction until they are deposited on the seabed.
Over time, so much sediment is deposited that a narrow strip of land (spit) forms across part of the bay/estuary.
How do mudflats/salt marshes form behind spits?
The shelter provided means that sediment is deposited behind it to form mudflats/salt marshes.
How are recurved/hooked spits formed?
As the spit grows longer, the tides, river currents and other wave directions turn the end of the spit into a hook.
How are double spits formed?
Where there are local variations in longshore drift and strong river currents. Spits form on either side of a large bay, but do not join as river currents pass out into the sea between the spits.
How are cuspate forelands formed?
It’s a low-lying, roughly triangular headland that probably develops when longshore drift from 2 opposite directions forms 2 spits across a bay. These meet and shelter the bay behind them, which fills with sediment. Mudflats and salt marshes form and deposition forms a new lowland area.
