Key terms Flashcards
What is erosion?
The wearing away of the Earth’s surface by the mechanical action of processes of glaciers, wind, rivers, marine waves and wind.
What is the fetch?
Refers to the distance of open water over which a wind blows uninterrupted by major land obstacles. The length of fetch helps to determine the magnitude and energy of the waves reaching the coast.
Define mass movement
The movement of material downhill under the influence of gravity, but may also be assisted by rainfall.
Define weathering
The breakdown and/or decay of rock at or near the Earth’s surface creating regolith that remains in situ until it is moved by later erosional processes. Weathering can be mechanical, biological/organic or chemical.
Define backwash
The action of water receding back down the beach towards the sea.
Describe constructive waves
Waves with a low wave height but with a long wavelength and low frequency of around 6-8/min. Their swash tends to be more powerful than their backwash and as a consequence beach material is built up.
Describe destructive waves
Waves with a high wave height with a steep form and high frequency (10-14/min). Their backwash is generally stronger than their swash, so more sediment is removed than is added.
Describe the process of longshore drift.
Where waves approach the shore at an angle and swash and backwash then transport material along the coast in the direction of the prevailing wind and waves.
Describe the process of wave refraction
When waves approach a coastline that is not a regular shape, they are refracted and become increasingly parallel to the coastline. The overall effect is that the waver energy becomes concentrated on the headland, causing greater erosion. The low energy waves spill into the bay, resulting in beach deposition.
What are tides?
The periodic rise and fall of the level of the sea in response to the gravitational pull of the sun and moon.
What is the coastal sediment budget?
The balance between sediment being added to and removed from the coastal system, that system being defined with each individual sediment cell.
Define high energy coasts
A coastline where strong, steady prevailing winds create high energy waves and the rate of erosion is greater than the rate of deposition.
Define low energy coasts
A coastline where wave energy is low and the rate of deposition often exceeds the rate of erosion of sediment.
What is a sediment cell?
A distinct area of coastline separated from other areas by well-defined boundaries, such as headlands and stretches of deep water
What are marine processes?
Operate upon a coastline and are connected with the sea, such as waves, tides and longshore drift.
What are sub-aerial processes?
Includes processes that slowly break down the coastline, weaken the underlying rocks and allow sudden movements or erosion to happen more easily. Material is broken down in situ, remaining in or near its original position. These may affect the shape of the coastline, and include weathering, mass movement and run-off.
Define hydraulic action
The impact on rocks of the sheer force of the water itself. This can exert enormous pressure upon a rock surface thus weakening it. Such activity is sometimes referred to as wave pounding.
What is wave quarrying?
A breaking wave traps air as it hits a cliff face. The force of water compresses this air into any gap in the rock face, creating enormous pressure within the fissure or joint. As the water pulls back, there is an explosive effect of the air under pressure being released. The overall effect of his over time is to weaken the cliff face. Storms may then remove large chunks of it.
Define abrasion
The material the sea has picked up also wears away rock faces. Sand, shingle and boulders hurled against a cliff line will do enormous damage. This is also apparent on inter-tidal rock plat
Define attrition
The rocks in the sea which carry out abrasion are slowly worn down into smaller and more rounded pieces.
Define solution
The dissolving of calcium-based rocks.
Define traction
Large stones and boulders are rolled and slid along the seabed and beach by moving seawater. This happens in high energy environments.
Define saltation
Small stones bounce or leapfrog along the relatively high energy conditions. Small particles may be thrust up from the sea bed only to fall back to the bottom again. As these particles land they in turn dislodge other particles upwards, causing more such bouncing movements to take place.
Define suspension
Very small particles of sand and silt are carried along y the moving water. Such material is not only carried but is also picked up, mainly through the turbulence that exists in the turbulence that exists in the water. Large amounts of suspended load, especially near estuaries, can cause a milky or murky appearance of the sea.
What is a spring tide?
When the moon and the sun are aligned. High tides are higher than average and low tides are lower than average. This is a tide which the difference between high and low tide is greatest.
What is a neap tide?
Sun and moon are right angles to each other. High tides are a little lower than average and low tides are a little higher than average.
