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Coasts
| Question | Answer |
|---|---|
| Wave frequency | the number of waves per minute. |
| Wave crest | the highest part of the wave. |
| Wave trough | the lowest part of the wave. |
| Wave steepness | the ratio of the wave height to the wave length (note that this cannot be steeper than 1:7 as this is where the wave breaks). |
| Wave period | the time taken for a wave to travel between one wave length. |
| Wave energy | E is proportional to LH^2 where L is wavelength and H is height. A small increase in wave height will result in a large increase in energy. |
| Diurnal range | the difference between the lowest temperature and the highest temperature in a 24-hour period. |
| Solution | the dissolving action of water on rocks, particularly carbonate rocks such as limestone. |
| Acid rain | a broad term used to describe several ways that acids fall out of the atmosphere. A more precise term is acid deposition, which has two parts: wet and dry. |
| Wind velocity | wind speed. |
| Duration | period of time during which the wind blew. |
| Fetch | Distance over which the wind blew. |
| Wavelength | the distance between two successive crests. |
| Swash | A translation of energy up in the beach in the form of a mass of foaming water. |
| Backswash | The return of water back down the beach as a result of gravitational pull. |
| Constructive waves | associated with swell and are characterised by longer wavelengths and lower height and wave frequency. The swash on these waves is greater than the backswash, as the spilling water has time to percolate on the beach. |
| Destructive waves | more often associated with storm conditions and have a steeper, shorter wavelength with more frequent waves. They produce a strong backswash which is capable of moving sediment downslope and impeding incoming waves. |
| Freeze-thaw | is the process whereby water repeatedly freezes and melts within joints/ cracks in rocks in areas where the diurnal range hovers around 0oC, eg.g. in the Scottish Highlands. |
| Pressure release | pccurs when jointed rocks have the pressure of any overburden removed and expansion can further open up joints/ cracks to weathering. |
| Biological weathering | refers to weathering resulting from organic agents. |
| Chemical weathering | tends to occur where there is alternate wetting and drying and/or towards the bottom of slopes where material and moisture often accumulate. |
| Oxidation | where rocks are exposed to oxygen in the air or water, e.g. where ferrous iron is changed by the addition of oxygen into the ferric state and appears a rusty colour. |
| Hydration | where rocks that may include salts absorb water and swell, making them more susceptible to decomposition. |
| Hydrolysis | a common form of weathering leading to decomposition. The H positive and OH negative ions in water combine with ions in the minerals found in rocks. |
| Carbonation | carbon dioxide in solution foundin rainwater produce carbonic acid. This attacks the calcium carbonate found in limestones and many other rocks, with the soluble product being washed away. |
| Longshore drift | the current resulting from wave crests hitting the beach at an angle, which is responsible for moving large amounts of sediment along the coast. |
| Dunes | formed when strong winds lift sediment off the beach and spit and propel them inland. |
| Bar | when a spit develops to cut off an embayment, perhaps creating a lagoon. |
| Tombolo | where ridges of sand and shingle link the coast to an island. |
| Embryo dunes | the first dunes to develop. |
| Isotatic change | land rise or fall. |
| Eustatic change | rising sea level. |
Created by:
apeploe
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