Coasts Key Words

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  • Created by: Ice_Fox
  • Created on: 08-03-22 11:35
System
A group of objects (abiotic and biotic) and the relationship between them
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Millennia
A time period of a thousand years
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Input
Material or energy coming into a system
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Output
Material or energy leaving a system
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Open system
Both input and outputs move within the boundaries of the system
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Kinetic energy
Energy of motion
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Potential energy
Stored energy from its position that is potentially transferable to another form of energy
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Thermal energy
Energy of heat
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Geomorphic Processes
Natural mechanisms that modify landforms on the Earth's surface
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Nearshore Zone
The area of a coastline between the point at which the waves start to break and the mean high tide line
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Evaporation
The process of water changing from a liquid form into a water vapour (a gaseous state)
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Throughputs
The amount of material passing through a system
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Longshore drift
The movement of sediment along a coastline as a result of a diagonal swash (parallel to the dominant wind direction) and the backwash (perpendicular to the coastline) by wave action
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Equilibrium
A system in long-term balance (inputs=outputs)
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Dynamic equilibrium
A system that has had varied average states over time as a result of an imbalance in inputs and outputs, and an adaptation to maintain equilibrium
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Negative feedback
An automatic response within a system triggered by a change that helps reduce the effects and restore equilibrium
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Sediment cell
A naturally occurring section of the coastline in which sediment circulates and there are very little inputs or outputs (largely self-contained). These are often determined by significant changes in the topography such as a headland (e.g. Land's End). The
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Closed system
A system where there is no transfer of material across the system's boarders
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Fetch
The distance of open water over which the wind can blow in one direction to form a wave before reaching the coast
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Aerolian processes
Natural mechanisms (erosion, transportation, deposition) caused by the wind
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Wave period
The amount of time it takes one wave cycle to pass a fixed point
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Swell waves
A relatively smooth wave that has travelled over a considerable distance before reaching the coast
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Storm waves
Large locally generated waves caused by high winds
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Swash
The movement of sediment up a beach, diagonal to the coastline but parallel to the dominant wind direction, due to incoming waves
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Backwash
The movement of sediment seaward, perpendicular to the coastline caused by outgoing waves
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Constructive wave
Swash is stronger than backwash so sediment is deposited creating an accumulation on the beach. Waves have a longer wave length
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Destructive waves
Backwash is stronger than swash causing a removal of sediment from a beach. Waves have a shorter wave length.
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Tide
The height of the ocean against the coastline determined by the alignment of the sun and the moon and the interaction of their gravitational pull
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Tidal range
The vertical difference between high and low tide over a tide cycle
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Lithology
The chemical and physical properties of a rock type
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Structure
The physical characteristics of rocks such as faulting, jointing, bedding...etc
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Planform
The shape/profile of a coastal landscape
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Shore-platform
A horizontal shelf of more resistant rock left behind by the marine erosion of the cliff behind
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Geo
A long, narrow, steep inlet cut into the coastline along a weakness such as a joint or fault
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Blowhole
A shaft in the cliff which, in storm conditions, can force sea water out above the cliff top
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Discordant coastline
A coastline with alternate bands of geology perpendicular to the coastline, resulting in differential rates of erosion
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Concordant coastline
A coastline with bands of geology parallel to the shore
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Rip currents
Strong narrow currents going seaward against breaking waves
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Cusps
A regular pattern of crescent shaped formations of sediment on a beach
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Ocean currents
Large-scale movement of sea water across the globe, driven by winds, and differences in temperature and salinity
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Sub-aerial processes
A sub-section of geomorphic processes that do not require a moving agent (such as water) and are land based

Weathering and mass movement
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Sediment budget
The net amount of movement of sediment entering and exiting a particular stretch of the coastline
Deficit means there are more outputs than inputs. Surplus is the opposite
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Weathering
The land-based in-situ wearing away and breaking down of rock
Can be physical, biological or chemical
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Freeze Thaw
The repeated freezing and melting of water (in a location with a large diurnal temperature range) in a rock joint, widening the crack until it eventually splits. Water expands by 9% when it freezes
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Pressure release
When overlying rock is removed, the underlying rock is able to release pressure created in their formation, forming fractures parallel to the surface
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Thermal expansion
The repeated process of rocks expanding when warm and contracting when cool, resulting in outer layers flaking off
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Salt crystalisation
The formation of salt crystals when water evaporates from saline sea water, that create pressure within porous rocks
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Chemical weathering
The in-situ breakdown of rocks as a result of chemical reactions between moisture and minerals in the rocks
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Oxidation
The reaction of oxygen (in rainwater or the air) with rocks containing certain minerals (iron is particularly susceptible)
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Carbonation
The reaction of carbon from the air with rainwater to form a weak carbonic acid, which reacts with limestone to form calcium bicarbonate. This is soluble. The reaction is reversible and this forms stalagmites and stalactites
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Solution
Certain types of rocks dissolving into water
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Hydrolysis
The reaction between water and certain minerals in the rocks which forms new minerals
(E.g. Feldspar in granite reacts with hydrogen in water to produce china clay)
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Hydration
The absorption of water by rocks causing them to expand and create pressure
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Tree roots
A type of biological weathering where roots of trees exploit cracks in the rocks and create pressure
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Organic acids
(Chelation)
The decomposition of organic matter may create an organic acid. This then reacts with minerals in the rocks
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Regolith
Loose layer of rocky material, often at the base of a cliff, formed by mass movement
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Rock fall
A type of mass movement where rock becomes separated from a slope and falls due to gravity
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Rock slide
A type of mass movement where rock slips in a linear movement along a slip plane
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Abrasion
The repeated hitting of loose rocks in the sea against the coast, wearing it away
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Attrition
Loose rocks in the ocean hit against each other making them smoother, rounder and smaller
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Hydraulic action
The repeated compression of air into a crack due to waves, increasing pressure, weakening the rock and causing the crack to widen
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Solution
(Transportation)
Carrying of dissolved minerals by the water
(Only deposited when the water evaporates)
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Suspension
Small particles are carried by water, making the water appear muddy
(Larger particles may be transported this way in storm conditions)
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Saltation
Irregular movement of medium sized particles (bouncing along the seabed)
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Traction
Irregular rolling or pushing movement of large particles by the ocean along the seabed
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Deposition
The dropping of sediment by water when it looses energy
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Settling velocity
The speed required for particles to be deposited
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Levees
A build up of sediment (ridges) either side of a river bank or stream channel that increases its capacity
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Crevasse splays
Low lying areas between levees
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Flocculation
The clumping of sediment due to salt into larger masses which are too heavy to remain suspended
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Strata
Horizontal layers in sedimentary rock due to its formation
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Bay
A concave shape/indentation in the coastline often between two headlands formed by erosion of less resistant rock (most commonly found on discordant cosatlines)
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Headland
A section of the coastline, further seaward than the rest, due to its more resistant geology
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Wave refraction
The reorientation of waves to align with the coastline (which focuses their energy on the headlands and dissipate in the bays) due to friction with the sea bed as it comes near the shore
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Orthogonals
Theoretical lines perpendicular to the wave fronts that indicate the transfer of energy of a wave
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Cave
A section of the coastline eroded by waves that forms an alcove or tunnel-like hole in a cliff or headland
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Arch
A cave that has reached the other side of the headland creating an open passage through
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Stack
The remainder of an arch once the overhead section has collapsed due to sub-aerial processes
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Stump
Smaller than a stack due to weathering, often only visible at low tide
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Runnels
A ridge of sediment parallel to the shore in the foreshore zone
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Berms
A ridge of sediment that forms at the mean high tide mark
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Cusps
Small, semi-circular indentations on a beach
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Spit
A build-up of sediment with the appearance of a long, thin beach extending from the coastline
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Onshore bars
A build-up of sediment that connects two headlands
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Tombolos
A spit that connects the mainland to an offshore island
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Salt marshes
Vegetated, saline areas formed in a low energy coastal area such as an estuary or behind a spit
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Turbid
Cloudy or muddy water containing sediment
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Saltpans
Flat areas of ground covered with salt from evaporated saline water
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Flocs
A collection of sediment due to flocculation (sediment clumping due to saline water)
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Delta
A build-up of sediment at an estuary
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Distributaries
Streams that branch off from the main river
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Eustatic change
A global change in sea levels due to changes in ocean water volumes
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Isostatic change
Localised change in sea levels often due to uplift of the crust
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Emergent landforms
Landforms that formed by wave processes during higher sea levels
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Raised beaches
Relic shore platforms higher than current sea levels
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Rias
Submerged river valleys
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Fjords
Submerged glacial valleys
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Sea wall
A form of coastal defence often made of concrete designed to reflect wave energy
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Groynes
Barriers along a beach or coastline, perpendicular to the coastline that traps sediment and slows down longshore drift
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Rip rap
Large boulders placed on coastlines to dissipate and reduce wave energy to slow erosion
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Gabions
Large cages full of rocks on a coastline to dissipate and reduce wave energy
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Hard engineering
Construction of coastal defences (often expensive) to reduce erosion
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Soft engineering
More natural methods of coastal defence (often cheaper) to reduce erosion
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Beach recharge
Adding sediment to a depleted beach to usual increase the natural coastal defence
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Other cards in this set

Card 2

Front

Millennia

Back

A time period of a thousand years

Card 3

Front

Input

Back

Preview of the front of card 3

Card 4

Front

Output

Back

Preview of the front of card 4

Card 5

Front

Open system

Back

Preview of the front of card 5
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