Coasts Flashcards
What is a constructive wave?
Stronger swash, weaker backwash, push material up the beach
What is a destructive wave?
Weak swash, stronger backwash, erode beaches
Why is sediment dropped in coastal areas?
Waves have low energy, so can’t carry the sediment any longer and drop it.
What is longshore drift?
Movement of material along the coast by waves which approach at a angle to the shore but recede directly away from it.
Describe the formation of a waterfall:
.When horizontal bands of hard rock are positioned over exposed less resistant soft rock, a step is created.
.As erosion continues the hard undercuts to form a overhang. Abrasion and hydraulic action contribute to erosion and create a plunge pool, overtime this gets bigger, increasing the size of the overhang until the hard rock is no longer supported so it collapses.
.This process continues and it retreats upstream.
. A steep sided valley is left where the waterfall once was. This is called a gorge
How is a headland formed?
When softer rock is eroded inwards, the hard rock sticks out into the sea, forming a headland
How is a bay formed?
Bands of soft rock such as clay and sand are weaker therefore they can be eroded quickly, so move back and form a bay with headlands of harder rock either side of it.
How is a stack formed?
. Cracks in headlands form and are widened due to hydraulic action and abrasion and eventually form a cave.
. The cave becomes larger and eventually breaks through the headland to from a arch.
. The base of the arch becomes wider with further erosion until it becomes too heavy and collapses into the sea.
. This leaves a stack. The stack then is undercut at the base until it collapses to form a stump.
What are groynes?
Wooden or rock structures built perpendicular to the shore, they trap sediment and help build up beaches by interrupting longshore drift.
What is rock armour?
Using boulders are the start of a beach to absorb energy given by the waves and dissipate it and stop erosion
What is beach nourishment? ( soft engineering )
Adding sand to the beach to widen it and reduce erosion to the land by the beach taking most of the erosion from the wave energy
What are sea walls?
Reflect the energy of waves and divert them away from the coastline, reducing erosion.
