8.1 Coastal processes Flashcards
Fetch
The distance of sea over which the wind can blow. Coastlines which face a larger ocean have larger fetch.
Wave crest
The top of the wave
Wave trough
The low point between two wave crests
Wave height
The difference in height between a wave crest and a wave trough
Wave length
The distance between two wave crests
Wave period
The time taken for a wave to travel through one wave length
Wave velocity
The speed of movement of the wave crest
Wave frequency
The number of waves that break on the beach in a given period of time
Wave energy
Directly related to wave height. Wave energy is released when the wave breaks.
Plunge line
The point at which the wave breaks
Swash
The body of foaming water that rushes up the beach when a wave breaks. It obtains its energy from the energy released by the breaking wave.
Backwash
The water which returns down the beach after a wave has broken.
Storm waves
Large waves, produced by strong winds, blowing from the ocean directly onto the coastline.
Plunging breakers
When storm waves break, they become vertical and plunge down onto the beach.
Destructive waves
Waves that remove sediment from a beach. They are steep, high waves that have a short wavelength and a high wave frequency. They have a weak swash and strong backwash.
Swell waves
If the wind that created the waves dies down over the ocean, the waves will continue to move in the same direction until they reach the coastline. When they reach the shore they will break gently.
Surging breakers
A breaking wave that slides or surges up the beach.
Constructive waves
Low, gentle waves that add sediment to a beach. They have a long wavelength and a low wave frequency. They have a strong swash and weak backwash.
Berms
Ridges which form at the top of the beach, running parallel to the coastline. They are usually made of stones or shingle and are produced by the fortnightly spring tide.
Orthogonals
Lines drawn at right angles to the wave crests as they approach the shore. They show how wave energy is concentrated or dispersed.
Blowhole
A tube that grows upwards through the rocks from the roof of the cave. It is caused by wave quarrying and slowly erodes upwards along a weakness in the rock and eventually breaks through at the top of the cliff.
Exfoliation
Weathering process which causes rock surfaces to peel.. Caused by expansion and contraction of surface layers of rock on the cliff face.
Oxidation
Process of chemical weathering, particularly affecting iron minerals where there is addition of oxygen to a mineral.
Halophytic
Salt-loving
Storm beach
The top of the beach, formed by stones and pebbles thrown up by strong waves during a storm.
Cuspate tombolo
When wave refraction causes LSD to operate in opposite directions either side of an offshore island, the beach extends out to the island, joining it to the mainland at low tide.
Sediment cells
Inputs, outputs and movements of sediment within an area.
