origin and development of landforms of coastal deposition Flashcards
where do depositional landforms occur
occur on coastlines where sand and shingle accumulates faster than its removed often takes place where the waves are low energy and there is an abundant supply of sediment
where are beaches found
found at the point where the land meets the sea and represents an accumulation of sediment
particle size on beaches is usually very small what happens because of the small sediment
when the small particles become wet they compact and allow little percolation. most of the swash is therefore returned as backwash little energy is lost to friction and material is carried down the beach which creates ridges and runnels at the low water mark.
what happens is sediment size is larger.
there is a steeper gradient this is because water rapidly percolates through shingle so backwash is limited meaning little is eroded from the beach.
what is bellow the storm beach
a series of ridges marking the successively lower high tides called berms
what will strong swash at spring tides create
storm beach
what are cusps
they are semi-circular-shaped depressions which form when waves break directly on to the beach usually where sand and shingle meet.
what are the characteristics of swash aligned beaches
experience minimal longshore drift and can be found on irregular coastlines where longshore drift is impeded and waves hit sections of the coast head on
what are the characteristics of drift aligned beaches
can have considerable amounts of sediment transported along them develop where the coastline is fairly regular and can extend out from the coastline if there is a sudden change in direction
what is a spit
it is an elongated, narrow ridge of land that has one end joined to the mainland and projects out into the sea or an estuary. it is composed of sand and shingle
how is a spit formed
where a coastline changes direction material from longshore drift will carry on being deposited past the headland above the high water mark. finer material is transported further and as the water loses its capacity to transport it further is deposited extending the spit towards the end of the spit the second most dominant wind direction recurves the end. e.g. Spurn Head
how can sand dunes develop on spits
as spits mature sand dunes develop as deposited sand dries out and is blown to the landward side of the spit where it accumulates and becomes stabilised by marram grass
salt marshes develop behind spits, why?
a more sheltered area between land and the spit is created low energy waves deposit finer material such as silt and clay. these deposits build up and are colonised by vegetation to become salt marshes.
what is a spit that joins an island to the mainland called
tombolo e.g. chesil beach
what is a spit that develops across a bay called
bar
