Flashcards in Coasts Deck (49):
what is the crest of a wave?
the top of the wave
what is backwash?
the movement of water and load back down the beach.
what is velocity?
the speed the wave is traveling at.
what is velocity influenced by?
wind, fetch and depth of water
what is the trough of a wave?
the low are between two waves.
what is the wave height?
the distance between two crests or two troughs
what is the wave frequency
the number of waver per minute
how are waves caused?
by wind blowing over the sea
what is wind strength?
the stronger the wind, the greater the friction, the larger the wave.
what is wind duration?
the amount of time the wind has been blowing
what is fetch?
the distance of open water over which the wind has been blowing. the longer the fetch the more powerful the wave.
what are constructive waves?
less energy and encourage deposition. Low in height ad widely spaced. Swash is stronger than the backwash. calm weather
what are destructive waves?
strong winds blown over large fetch areas. powerful ad lead to coastal erosion.
example of mechanical (physical) weathering?
what is freeze thaw weathering?
the repeated freezing and thawing of water in joints in a rock. wen water freezes it expands by about 10% putting pressure on the rock. when the ice melts it seeps deeper into the rock. after repeated cycles fragments of rock start to break off.
example of chemical weathering?
how does acid rain weather rocks?
when rain falls on rocks such as limestone a weak chemist reaction takes place causing the rocks to weaken and breakdown.
what is biological weathering?
when roots, burrowing animals and nesting birds get into the cracks they widen them causing the rock to weaken and decay.
what is mass movement?
the downslope movement of rocks and soil from the cliff top under the influence of gravity.
what are rock falls?
suddenly when pieces of rock from a weathered cliff fall. This often occurs when the rock at the base of the cliff has been undercut by the waves leaving the rocks above unsupported causing them to fall
what is slumping?
occurs after heavy rainfall The rain seeps into permeable rock. At the junction where the permeable rock meets the impermeable rock the saturated soil and weakened rock slumps and slides along a curved surface.
what is sliding?
large amounts of soil and rock move downslope rapidly. along a flat surface.
what is the land at beach head used for?
farming because the chalk is permeable
what is attrition?
materials carried by the waves bump into each other and so are smoothed and broken down into smaller particles.
what is hydraulic action?
the force of water against the coast. water in cracks compresses air causing cracks or explosions.
what is corrosion/solution
the chemical action of sea water. when the acids in the sea water slowly dissolve rocks in the coast.
what is abrasion/corrasion?
when the coast is worn down by material carried by the the waves. the waves throw these particles against the rock.
what is traction?
large pebbles roll along the seabed
what is saltation?
a hopping or bouncing motion of particles too heavy to be suspended.
what is suspension?
particles carried in the water.
what is solution?
what is longshore drift
when the backwash and swash carry particles up and down the beach.
what is a concordant coast?
a coastline where the geology runs parallel to the coast.
examples of concordant coasts?
lulworth cove, durdle door , dorset
what is a discordant coast?
a coastline when the bands of hard and soft rocks lie at right angles to the coastline.
examples of discordant coasts?
swanage bay. old harry rocks.
what is a headland?
an area of more resistant rock jutting out into the sea from the cliff line
what is a bay?
an area of land, curved in shape which has been eroded between two headlands
what us a wave cut platform?
the narrow, flat area often found that the base of a sea cliff or along a shoreline. obvious at low tide.
how are wave cut platforms made?
after destructive waves hit the cliff foot causing undercutting between the high and low water marks this creates a wave cut notch with enlarges into a cave. erosion causes the cave to increase until the cliff collapses. this leaves a wave cut platform.
what is a cave?
a hollow at the base of a cliff
what is an arch?
the rock bridge formed over a passage through a headland eroded by the waves.
what is a stack?
an isolated column of rock
what is a stump?
a short piece of rock found at the end of a headland, formed after a stack has collapsed.
where are the old harry rocks?
handfast point, isle of purbeck, dorset , southern England.
what rock type are the old harry made from?
what are spits?
a permanent land form resulting from marine deposition. one end attached to land. have a hooked or curved end from the and changing direction.
what are bars?
a ridge or barrier than stretches across a bay. only able to extend across a bay due to the abscence of a river.