Coasts Flashcards
(36 cards)
What are tide?
Regular rise and fall movement of sea levels
How are tides and waves formed/caused?
Tides are caused/ affected by the moon/gravity and waves are formed by wind
What indicates the direction to which the wave will hit the coast
direction of the wind
what are waves?
surface movements of water caused by the wind - with the exception of tsunami waves. waves represent the transfer of energy
What factors affect the size and energy of waves
- how long the wind has been blowing
- strength of the wind
- length of fetch; how long it has travelled
- prevailing wind
describe the swash movement of waves
as the wave reaches the shor, it breaks. the white foamy water that flows up the beach is the swash
describe the backwash movement of waves
when the water runs out of speed, it stops and flows back down the beach into the sea
what are characteristics of constructive waves
- strong wash and weak backwash
- calm weather
- limited energy; mostly used by swash
what are characteristics of destructive waves
- weak swash and strong backwash
- lots of erosion
- storm weather
- lots of energy
what are the types of erosion
hydraulic action, solution, attrition, abrasion
what is hydraulic action
the pure force of water hitting the coast and breaking
what is solution
when sea water dissolves certain types of rocks
what is attrition
when rocks that the sea is carrying are knocked against each other
what is abrasion
when pebbles and small rocks grind along a rock platform
how are cliffs formed?
- cliffs are formed by hydraulic action; is caused by air compression into the cracks deepening the notch and creating an overhanging side that collapses
- abrasion also takes place; waves are wearing out materials
- rocks are dissolved
- as the waves break into the coast, they cut a notch in a rock
- when the notch gets deeper, the rock collapses and this process continues and the coastline retreats inwards
what is a bay
a wide deep opening into the coastline
what is a headland
a piece of land projecting out into the sea
how are bays and headlands form
- different types of rocks occur along the coastline
- softer rocks are eroded quickly, creating the bay
- harder rocks are eroded slowly and so stick out onto the sea
how are caves, arches, stacks and stumps formed?
- the large crack (consequence of hydraulic action) grows into a cave
- the cave becomes larger and breaks to form an arch
- arch erodes and colapses, leaving a tall rock (aka stack)
- stack erodes and forms a stump
describe transportation of longshore drift
it moves the materials along the beach. this occurs when the waves approach the beach at an angle
describe transportation in swash and backwash
brings materials onto the beach when the backwash brings it back down to the sea in a straight line (forms a zig zag)
what is a sand dune
a sand dune is a hill of sand which form above the high tide level
how is a bar/ sand spit formed
It is formed due to longshore drift transporting sediment along the coastline.
how is a sand dune formed
wind dries the sand on the beach and it is then blown inland until it is trapped
