Coasts Key Words Flashcards
Abrasion/Corrasion
The wearing away of the shoreline by sediment, usually through friction, scraping, scouring and rubbing
Abandon the line
Withdrawal of human occupation in areas of risk. Often unpopular with farmers and property owners
Accretion
The accumulation of marine sediments. Where deposition exceeds erosion
Advance the line
Active intervention to produce a defensive line out at sea.
Arch
A raised area left when two caves erode back to back on a headland
Attrition
When particles are reduced in size and rounded by colliding with each other
Backwash
Movement of water back towards the sea after a wave has broken
Bar
Deposit of sediment extending across the mouth of a bay, sometimes reaching the other side and cutting it off
Berm
Low hill of sand that forms at the upper limit of the swash. They are short term features that are removed by tides and storms
Beach nourishment
Sand and shingle from elsewhere that is added to a beach to maintain its length and breadth to protect the coast
Blow-hole
A pipe leading from a cave up through a cliff to the surface
Breaching
Failure of defences allowing flooding by tidal or storm action
Char
An island formed at a river delta
Constructive waves
Low frequency (6-8 per minute) Produces a gentle beach gradient Powerful swash weak backwash High deposition Large wavelength
Concordant geology
The alignment of rock types that are parallel to the coastline
Corrosion
When carbonates dissolve in the water. Also when salt crystals evaporate and expand, causing the rock to disintegrate
Cusp
Crescent shaped depressions formed between varying sediments (sand and shingle) formed by a strong swash and backwash
Cuspate Foreland
A triangular accumulation of sediment along the coastline formed by longshore drift in opposing directions
Deltas
When the sediment delivered to the mouth of a river exceeds sediment removed a delta is formed
Destructive waves
High frequency (10-14 per minute) Strong backwash weak swash Steeper beach profile High erosion Short wavelength
Discordant geology
When the rock type runs perpendicular to the coastline
Do nothing
Where no action is taken to protect the coast
Downdrift
The direction of the net longshore drift
Dunes
Mound like landforms composed of sand that has been blown off the beach by onshore wind. Embryo dunes > foredunes > yellow dunes > grey dunes > wasting dunes
Eustatic
Changes in sea level, usually on a global scale, due to variations in the amount of water in the oceans
Fetch
The distance of uninterrupted water surface over which the wind has blown to form waves. A greater fetch increased energy
Fjord
Very deep u shaped estuaries formed by the drowning of glaciated valleys
Flood
temporary excess of water that spills over onto land
Flood Frequency
How often a flood occurs
Gabions
Cages enclosing rocks to defend the coast
Geo
Steep sided narrow inlet
Groyne
Posts and boards that run perpendicular to the coastline to trap eminent drift along the shore
Halophytes
Plants that can tolerate salty conditions
Hard engineering
Structures engineered to protect cliffs from erosion
Hold the line
Taking action to maintain the current position of the coastline
Hydraulic action
Force exerted by moving water
Isostatic
Changes in sea level, usually on a local scale, due to the rise and fall of land masses
Isthmus
A narrow piece of land connecting two larger pieces of land
Longshore drift
Movement of sediment in a zig-zag pattern Downdrift
Magnitude
The size of a flood
Managed retreat
The deliberate re-establishment of the line of defence inland and allowing the original coastline to be breached
Mass movement
Sub aerial process where gravity, usually along with rain, causes material from the coastline to move down the cliff
Psammosere
Successions of stages of plant growth, found at sand dunes
Recession
With coasts, it is when a coastline retreats
Retreat the line
Intervention to set back the line of defences
Revetment
Defences aligned parallel to the coastline
Ria
A river valley that has been drowned, usually by sea level rise
Runnel
Ridges in the beach which form In strong backwash. Runnels separate pools of water at the low tide level
Saltation
Sand bounces across the surface of the beach blown by wind
Sediment cell
A length of coastline that is relatively self contained as far as the movement of sand and shingle is concerned
Sediment sink
Point or area where sediment is irretrievably lost from a coastal cell, such as an estuary
Slumping
When the base of the cliff is undercut and material slides down the cliff face
Soft engineering
Protecting coastlines using more natural methods
Spit
Long ridges of sand and shingle that is connected to land at one end
Spring tide
Particularly high or low tides caused when the Sun, Moon and Earth are in alignment.
Surges
Changes in water level as a result of meteorological forces, like storm surges
Swash
Movement of water up a beach away from the sea as a wave reaches the shore
Swell
A circular motion caused by wind in the open sea which is non-moving
Tidal range
The variation from mean water level between high and low water mark
Tombolo
Shingle ridge linking island to mainland
Updrift
The direction opposite to predominant longshore drift
Wave cut platform
A flat rock area in the intertidal zone created by a succession of wave cut notches, where the cliff has collapsed
Wave crest
The highest point of a wave
Wave energy
Energy= wavelength x wave height x 2
Wavelength
The distance between two successive crests
Wave period
The time for a wave to travel one wavelength
Wave steepness
The ratio between wave height and wavelength
Wave refraction
As waves enter shallow water they are affected by friction, if they meet a headland they curve towards the headland, in a bay the waves spread out and dissipate
Wave trough
The lowest point of a wave
Weathering
The breakdown of rocks in situ (in their original location without them being moved). This produces finer particles
