Coasts EQ2 Flashcards
(29 cards)
What are constructive and deconstructive waves?
Deconstructive waves have a weak swash and strong backwash.
Constructive waves have a strong swash and weak backwash.
What is hydraulic action?
Shear power of the waves wear away the cliff face.
What is abrasion?
Known as corrasion. Waves break at the base of the cliff, throwing sediment at it.
What is attrition?
Rocks hit each other, forming smaller, rounder rocks.
What is corrosion?
Also known as solution. Rock particles dissolve due to weak alkaline waters.
How is a wave cut notch and platform formed?
1) The sea attacks the base of the cliff between the high and low water mark.
2) A wave-cut notch is formed by erosional processes such as abrasion and hydraulic action - this is a dent in the cliff usually at the level of high tide.
3) As the notch increases in size, the cliff becomes unstable and collapses, leading to the retreat of the cliff face.
4) The backwash carries away the eroded material, leaving a wave-cut platform.
5) The process repeats. The cliff continues to retreat.
What is the cave, arch, stack, stump sequence?
1) Cracks are widened in the headland through the erosional processes of hydraulic action and abrasion.
As the waves continue to grind away at the crack, it begins to open up to form a cave.
2) The cave becomes larger and eventually breaks through the headland to form an arch.
3) The base of the arch continually becomes wider through further erosion, until its roof becomes too heavy and collapses into the sea. This leaves a stack (an isolated column of rock).
4) The stack is undercut at the base until it collapses to form a stump.
How do headlands and bays form?
Bands of soft rock such as clay and sand are weaker therefore they can be eroded quickly. This process forms bays. A bay is an inlet of the sea where the land curves inwards, usually with a beach. Hard rock such as chalk is more resistant to the processes of erosion. When the softer rock is eroded inwards, the hard rock sticks out into the sea, forming a headland.
What is traction?
Large and heavy rocks roll along the seabed.
What is saltation?
Smaller, lighter rocks bounce along the seabed.
What is suspension?
Lighter sediment is carried by the flow of water.
What is solution?
Dissolved sediment carried by the flow of water.
What’s the process of longshore drift?
The movement of material along the shore by waves. It happens when the waves approach the beach at an angle. The swash carries material up the beach.
How are spits formed?
An extended stretch of sand or shingle jutting out in the sea from the land. Form drift-aligned beaches. Sand and shingle are moved along the coast by longshore drift. If the coastline changes direction, sediment will build up and become deposited (e.g. due to an estuary mouth), forming a spit. The outward flow of the river will prevent the spit from extending the full width of an estuary. The end of the spit curves round and carries the material around behind the spit which is known as a recurved spit and forms salt marshes behind them.
e.g. Spurn head
How are offshore bars formed?
Long ridge of sand or pebbles formed a short distance out to sea parallel to the coast in an offshore zone. They form from sediment eroded by destructive waves and carried seawards by backwash.
How are swash aligned beaches formed?
Form in low energy environments e.g. bays. Sediment moves up the beach with lateral transfer. They tend to form curved concave beaches. The beach face is orientated parallel to the fronts of dominant waves.
e.g Chesil beach in Dorset
How are drift aligned beaches formed?
Forms when waves approach the coast at an angle. Sediment transferred by longshore drift along the coast. Often form a spit.
How are barrier beaches formes?
Where a spit or beach extends across a bay to join two headlands. Formed from rounded shingle deposited. Barrier beaches can trap lagoons behind them.
How is a tombolo formed?
A tombolo is formed when a spit connects the mainland coast to an island. A spit is a feature that is formed through deposition of material at coastlines. The process of longshore drift occurs and this moves material along the coastline.
Through this process material is constantly moved along the coastline. When the coastline changes direction or there is a river estuary the process of longshore drift continues. This causes the material to be deposited in a long thin strip that is not attached to the coast and is known as a spit. If this feature moves in the island’s direction and connects it to the mainland, it becomes a tombolo.
How are double spits formed?
Double spits are where two spits extend out in opposite directions from both sides of the bay, towards the middle. They form where longshore drift is operating in different directions on opposite sides of the bay.
How are cuspate forelands created?
A cuspate foreland is a triangular-shaped headland that extends out from the main coastline. It occurs where the coast is exposed to longshore drift from opposite directions. Sediment is deposited at the point where the two meet which forms a natural triangular shape as it builds up. Vegetation begins to grow on the deposited sediment, it helps to stabilise the landform and protect it from storms that could erode. Cuspate forelands can be smaller or they can be larger features.
What is mechanical weathering?
What is biological weathering?
What is chemical weathering?
Also known as freeze thaw. Occurs when water enters a crack or joint. Then freezes in cold weather. It expands about 10%, it exerts pressure, forcing the rock apart.
The process in which plants, animals and bacteria break down rocks into smaller pieces.
Erosion of rocks caused by a chemical reaction e.g carbonation.
What is mass movement and the different categories?
Movement of surface material caused by gravity.
Flows and slides.
What is soil creep?
Slow down-slope movement of earth materials under the influence of gravitation.
