Coastal Landscapes and Processes Flashcards
(45 cards)
What are the three types of weathering?
Mechanical, chemical and biological weathering.
What is mechanical weathering?
Freeze-thaw weathering, a type of mechanical weathering, occurs when water gets into cracks in rocks. When the temperature falls below freezing, the water will expand as it turns into ice. The expansion puts pressure on the rock around it and fragments of the rock may break off. This type of weathering is common in highland areas where the temperature is below freezing in the night.
What is chemical weathering?
Rainwater contains weak acids that can react with certain rocks. Carbonates in limestone are dissolved by these weak acids and this causes the rock to break up or disintegrate. This can be seen on limestone statues and pavements.
What is biological weathering?
This is the action of plants and animals on the land.
Seeds that fall into cracks in rocks will grow in the presence of moisture, and breaking up the rocks as they grow.
Burrowing animals like rabbits can further break up rocks by making tunnels.
What is mass movement?
When material moves down a slope due to the pull of gravity.
Where is mass movement common in coasts?
Clay cliffs - in dry weather the clay contracts and forms cracks and when it rains water gets into these cracks, weakening the rock until, due to the pull of gravity, they fall off.
What are the four processes of coastal erosion?
Abrasion, hydraulic action, solution and attrition.
What is abrasion?
Where sand and pebbles carried within waves are thrown against the cliff face with force, and particles break off of the rock face as a result, which are in turn used to repeat the process.
What is hydraulic action?
This is the pressure of the water being thrown against the cliff by the wave. It also includes the compression of air in the cracks, as water gets into the cracks, it puts a large amount of pressure on the rock, causing pieces of rock to break off under the pressure.
What is solution?
This is a chemical reaction between rocks and the salt and other acids in the water. This is evident on limestone cliffs, where the water is milky blue due to the dissolved lime.
What is attrition?
This process involves wearing away rocks that are at sea. As the boulders in the sea continually roll around, they chip away at each other until smooth pebbles or sand are formed.
What are the four ways that the sea transports materials?
Traction, saltation, suspension and solution.
What is traction?
This is where large sediment such as pebbles roll long the sea bed.
What is saltation?
Where small pieces of shingle or large grains of sand are bounced along the sea bed.
What is suspension?
Where small particles like sand and clay are carried in the water; this can make the water cloudy, especially during storms or when the sea has a lot of energy.
What is solution? (In the context of transport)
Where minerals are dissolved in sea water and carried by the sea water.
What is the process of longshore drift?
The movement of sand and pebbles down a coastline. The direction of the waves hitting the coastline is determined by the prevailing wind. If the wind is blowing at an angle, the swash will approach at this angle, transporting the pebbles and sand with them. As the backwash is being pulled by gravity, it will find the shortest route down the beach. It always returns at 90 degrees relative to the coast.
What is deposition?
Deposition is laying down materials like sand and pebbles, which are being transported by the sea. The sea will deposit materials when it slows down and loses energy.
How does a rock’s structure affect erosion rates?
Rocks that are well jointed or have many faults, such as limestone, will erode rapidly since the waves exploit these lines of weakness. Rocks that have fewer joints will be harder to erode, rocks like chalk have lines of weakness that allow the sea to erode them easily.
What is a concordant coastline?
Concordant coastlines have rocks that lie parallel to the coastline. These have alternate layers of hard rock and soft rock, the hard rock will act as a barrier to the erosive power of the sea. If the sea erodes the hard rock, the soft rock behind it will quickly erode afterwards.
What is a discordant coastline?
Discordant coastlines have bands of rock that lie at right angles to the coastline. If there are alternate layers of hard and soft rock, the soft rock will erode faster, forming bays, with the resistive rocks forming headlands.
What is a destructive wave?
They are the most important agent in erosion and take sediment away from coastlines. The backwash is stronger than the swash and therefore it is able to carry sand and pebbles away from the shore. They break frequently and are normally found on steep beaches.
What is a constructive wave?
They are responsible for deposition in coastal areas and landforms. The swash is more powerful than the backwash and therefore it deposits material. They break infrequently and are generally found on gently sloping beaches.
What landforms do destructive waves create?
Headlands, bays, caves, arches, cliffs, stacks and wave-cut platforms.
