2B.5 sediment transport + deposition Flashcards
(23 cards)
what is traction
when larger sediment like pebbles and boulders roll along, pushed by waves and currents.
what is saltation
sand sized particles which bounce along either due to the force of water or wind.
what is suspension
the lightest sediment (silt and clay) are carried along in the water column
what is solution
transport of dissolved material carried in the water
outline longshore drift
the zigzag movement of sediment along a beach. the wind blows the waves at an oblique angle so the swash pushes sediment up the beach at an angle. the backwash is affected by gravity so returns down slope at a perpendicular angle.
what are some problems with long shore drift
too much beach sediment is moved along the coast so the beach elsewhere is depleted of its sand or shingle.
what is deposition
when the force transporting sediment drops.
what are the two types of deposition
gravity settling
flocculation
what is gravity settling
occurs when the energy of transporting water becomes too low to move sediment. large sediment will be deposited first followed by smaller sediment
what is flocculation?
a depositional process that is important for small particles like clay, which are so small they remain suspended. clay particles clump together due to electrical or chemical attraction and become large enough to sink
how is a beach formed
accumulations of sand or shingle found in the foreshore and backshore zones. produced by material deposited by construcitve waves. the swash has the strength to carry material up the beach, but backwash only has enough energy to transport some material back down the beach, leaving the remained deposited
how is a spit formed?
form when the coastline changes direction and longshore drift continues to move material along the beach in the original direcion. LSD will deposit material in the sea after the coastline had changed direction. over time the level of sand deposited will build-up until it is above sea level. the seaward end is called the distal end.
what is a recurved spit
a hook or recurve may form at the end of the spit. this is because wave refraction round the distal end transports and deposits sediment for a short distance in the landward direction. alternatively it could be because the wind and wave front are frequently at an opposing angle.
what is an offshore bar
forms when sediment is transported on and off a beach. destructive waves remove sediment from the beach and form the offshore bar. constructive waves transport material from the offshore bar back onto the beach. ridges of sand or shingle run parallel to the coast in an offshore zone. they form from sediment eroded by destructive waves and carried seawards by backwash.
what is a barrier beach and bar
where spits are joined to the mainland at both ends, trapping water behind in a lagoon
what is a tombolo
formed by wave refraction and diffraction. as waves near an island, they are slowed by the shallow water surrounding it, these waves then bend around the island to the opposite side as they approach.
what is a cuspate foreland
found on coastlines and lakeshores that are created by lsd. formed by accumulation and progradation of sand and shingle, they extend outwards from the shoreline in a triangular shape
what are the inputs of a sediment cell
where sediment is made- cliffs or eroding sand dunes. some sources are offshore bars and river systems.
what are the transport of the sediment cell
sediment moving along the shore, swash, backwash, longshore drift, tidal currents, sea/ocean currents, wind
what are the outputs of the sediment cell
sinks, where the dominant process is creation of depositional landforms. spits, offshore bars, sand dunes, beaches, bars, barrier islands.
what is the sediment cell case study
from Portland Bill to Selsey Bill
what is the geology of the portland bill / selsey bill area
sedimentary bedrock: sand, silt, clay. low resistance. less resistant at selsey bill
