Coastal Processes Flashcards
What is abrasion?
The process of rocks and other debris being carried by waves and grinding down a cliff surface as a result of repeated impact.
What is attrition?
The process of rocks hitting into one another - due to wave action - and becoming broken down and more refined.
What is climate change?
A change in global or regional climate patterns, in particular a change apparent from the mid to late 20th century onwards and attributed largely to the increased levels of atmospheric carbon dioxide produced by the use of fossil fuels.
What are the main two types of waves and their differences?
Destructive: They occur when wave energy is high and the wave has travelled over a long fetch. They tend to erode the coast. They have a stronger backwash than swash. They have a short wave length and are high and steep.
Constructive: They break on the shore and deposit material, building up beaches. They have a swash that is stronger than the backwash. They have a long wavelength, and are low in height.
What is corrosion?
Acids contained in sea water will dissolve some types of rock such as chalk or limestone.
Evaluate eustatic and isostatic change.
Eustatic: water level rise or fall
Isostatic: land level rise or fall
What is fetch and how does it affect wave energy?
The distance over which wind has travelled over a wave and so in turn, the distance over which a wave has travelled. A larger fetch produces waves of higher energy as the waves have travelled further and had a larger input of wind energy and so gained more momentum.
What is hydraulic action?
Air may become trapped in joints and cracks on a cliff face. When a wave breaks, the trapped air is compressed which weakens the cliff and causes erosion. This erosion is called cavitation.
What is longshore drift and what causes it to happen?
Waves can approach the coast at an angle because of the direction of the prevailing wind. The swash of the waves carries material up the beach at an angle. The backwash then flows back to the sea in a straight line at 90°. This movement of material is called transportation.
Continual swash and backwash transports material sideways along the coast. This movement of material is called longshore drift and occurs in a zigzag.
What is saltation?
Load is bounced along the sea bed, eg small pieces of shingle or large sand grains. Currents cannot keep the larger and heavier sediment afloat for long periods. This bouncing of material can also occur onshore with sand particles.
What is suspension?
Small particles are carried in water, eg silts and clays, which can make the water look cloudy. Currents pick up large amounts of sediment in suspension during a storm, when strong winds generate high energy waves.
What is traction?
The rolling of larger particles that cannot float or bounce along the seabed due to the force of currents and waves.
What causes a storm surge and what is a storm surge?
Storm surge is the rising of the sea level due to the low pressure, high winds, and high waves associated with a hurricane/storm as it makes landfall. The storm surge can cause significant flooding and cost people their lives if they’re caught unexpected
What is a sediment cell?
Sediment cells are areas along the coastline and in the nearshore area where the movement of material is largely self-contained. They can be considered as a closed coastal sub-system as far as sediment is concerned.
What is positive and negative feedback regarding sediment cells (with reference to equilibrium)?
Negative feedback is a stabilising mechanism acting to oppose changes to coastal morphology and establish equilibrium. A coastal environment in equilibrium is able to dissipate or reflect incoming energy without the occurrence of sediment input or output and change to morphology. For example; when a beach in equilibrium erodes during a storm it forms an offshore bar that in turn forces waves to break over it. By doing this the waves lose a lot of energy and dissipate before reaching the shoreline, significantly reducing further erosion. When the storm calms, the bar is then re-worked back onto the beach.
In contrast positive feedback pushes a coastal system away from equilibrium by modifying its morphology until a threshold is reached, whereby a different type of response occurs. For example; if a storm event was to breach the foredune of a beach that is not in equilibrium, a vulnerable area would be created, which in turn would become susceptible to the formation of a blowout due to wind exploiting the absence of vegetation.
What is beach morphology?
The origin and evolution of coastal features.
What is swash and backwash?
When a wave breaks, water is washed up the beach - this is called the swash. Then the water runs back down the beach - this is called the backwash
What is wavelength?
The length of one whole wave (from crest to crest or trough to trough) in metres.
What are high and low energy coastlines?
Low: Low-energy coasts are coasts sheltered from storms and swells by adjacent topographical features (barrier island, reef, embayment, shoal, headland), by their position with respect to prevailing wind direction, by their position in a climatic belt, by gentle offshore topography, or by a combination of these factors.
High: High-energy coasts are those that are exposed to strong, steady, zonal winds and fronts with high wave energies.
What is thermal expansion?
When water heats up, it expands. About half of the past century’s rise in sea level is attributable to warmer oceans simply occupying more space.
What is a plant succession?
Succession is a directional non-seasonal cumulative change in the types of plant species that occupy a given area through time. It involves the processes of colonization, establishment, and extinction which act on the participating plant species.
