Coasts Key Terms Flashcards
Landform
Individual features which are created by coastal processes (eg stacks, wave cut platforms and spits)
Landscapes
The entire area of sea, coastline and immediate land behind the sea front. This includes landforms
Tides
Periodic rises and fall in the level of sea caused by the gravitational pull of the sun and the moon
Spring tides
Bigger tide because the sun, moon, and earth are all on the same plane meaning the Sun and moons gravity are pulling Earths water in the same way. The sun adds to the moons pull
Neap tides
Smaller because the sun and the moon are at right angles to each other, meaning their gravity pulls in different directions
Tidal range
The deference in height between the low and high tide marks
Sediment cells
A stretch of coastline within sediment move,ent is more or less contained.
In total there are 11 cells around the UK, which are then divided into further sub cells
Geomorphology
Landform creating
Positive feedback
The rate of debris removal exceeds the rate of weathering and mass movement then a positive feedback can operate, as the rate of weathering and mass movement could increase
Negative feedback
If debris removal is slow and ineffective, there will be a build up of debris that reduces exposure of cliff face. Weathering and mass movement rates will decrease
Mass movement
The downhill movement of weathered material under the force of gravity
Traction
Large particles like boulders pushed along the sea bed by the force of the water
Saltation
Pebble sized particles are bounced along the seabed by the force of the water
Suspension
Small particles like silt and clay are carried along in the water
Solution
Soluble materials dissolved in the water and are carried along
Longshore drift
A key flow (transfer) within the coastal system and sediment cells. Involves the movement of material along a beach, usually at the angle of the prevailing wind
Concordant coastline
Rocks on these coastlines run parallel to the sea
Discordant coastline
Rocks on these coastlines run perpendicular you the sea
Swash aligned
When waves break parallel with the coast, the movement of water and material is largely up and down the beach
Drift aligned
Waves approach the coastline at an angle, the swash moves material up beach in that direction. The backwash returns at right angles
Spit
A long narrow feature that extends from the main land at the end of a drift aligned beach
Sand dunes
Accumulations of sand blown into mounds by the wind (aeolian)
Fluid threshold velocity
Speed the wind needs to be in order to move the sand
Pioneer species
Plants tolerant to salt and soaking of sea tides. They are the first species to arrive
Flocculation
Small particles binding together, then falling out the water
Halophytes
Plants that are tolerant of salt and the periodic soaking of the sea caused by the tide
Mudflats
Created by the deposition of fine silts and clays in sheltered low energy coastal environments such as estuaries
Saltmarsh
An area of coastal grassland that is regularly flooded by sea water
Eustatic change
A global change in sea level resulting from a fall or rise in the level of the sea
Isostatic change
Local changes in sea level resulting from the land rising and falling relative to the sea
Inputs
Things that enter the system from outside sources/ systems
Flows/ transfers
Processes of movement within a system
Stores/ components
Part of a system not necessarily in motion
Outputs
Material/ energy moving out of a system
Feedbacks
Can be positive (flows lead to increase/growth) or negative (flows lead to decrease/ decline)
Characteristics of constructive waves
Strong swash Weak backwash Add material to the coastline Never reach back of beach Low in proportion to length Formed by distant weather systems Causes depositional landforms
Characteristics of destructive waves
Weak swash Strong backwash Remove material from the coastline Causes cliffs face erosion Tall in relation to length Common during winter storms Break downwards with great force Causes erosion all landforms
Sources of coastal energy
Wind (steeper gradient, faster wind moves)
Waves
Current
Tides
Factors impacting wave energy
Strength of wind- stronger the wind, more energy is transferred to the waves, so larger waves form
The fetch- longer then wind travelled, more time for energy to transfer to the wave
Duration longer duration, more time for energy to transfer
Characteristic of a high energy coast
Rocky coastline
Contains cliffs and headlands
Erosion exceeds deposition
Characteristics of a low energy coastline
Less powerful waves Beaches and spots found here Sandy and estuarine Deposition exceeds erosion Sheltered areas (eg bays)
Sources of sediment: rivers
Rivers erode their banks and beds, this sediment then travels down the river and towards the coast, where it may be deposited
Sources of sediment: cliff erosion
When cliffs erode, a large amount of sediment falls to the beach below which can be moved by longshore drift and waves backwash
Sources of sediment: offshore sediment
Carried to coastline by onshore currents or constructive waves
Sources of sediment: wind
Wind blows small sediment, like sand, towards the ocean. The sediment can be used to form sand dunes
Factors determining weathering
Type of rock Temperature Amount of moisture Volume or type of vegetation Structure of the rock
Coastal weathering: biological
Thin plant roots grow into small cracks in a cliff. These widen as the root grows, which breaks the rock
Water running through decaying vegetation becomes acidic, which leads to increased chemical weathering
Birds and animals dig burrows into cliffs
Marine organisms are also capable of burrowing into rocks
Coastal weathering: chemical- carbonation
rainwater absorbs CO2 from the air to form a weak carbonic acid. This reacts with calcium carbonate in rocks. The cooler the rainwater, the more CO2 is absorbed
Coastal weathering: chemical- oxidation
Reaction of rock minerals with oxygen, to form a rusty red powder, leaving rocks vulnerable to weathering
Coastal weathering: chemical - solution
The dissolving of rock mineral, such as halite (rock salt)
Coastal weathering: mechanical (physical)- frost shattering
When water enters cracks and freezes (in cold weather). The volume expands (by 10%), which exerts more pressure to rocks and crack them more. May lead to parts breaking off.
Coastal weathering: mechanical (physical)- salt crystallisation
When salt water evaporates, crystals get left over time, which grows and adds pressure to rocks,causing parts to break off
Coastal weathering: mechanical (physical)- wetting and drying
Clay expands when wet and contracts when dry
Mass movement: soil creep/ solifluction
Slow movement of soil particles downhill. Particles rise due to wetting/ freezing
Nature movement: creep/ flow
Rate of movement: imperceptible
Wet
Mass movement: mudflow
Water gets trapped in rock, increasing pressure and causing particles to part.
Mature of movement: flow
Rate of movement: often rapid
Wet
Mass movement: run off
When overland flow occurs, small particles are moved down slope, to literal zone forming a input to sediment cell.
Nature of movement: flow
Rate of movement: rapid
Wet
Mass movement: Landslide/ debris/ slide/ slump/ slip
Rock moving rapidly down hill along a slide plane,
A land slip is the same, but it’s surface is curved rather than flat.
Nature of movement: slide
Rate of movement: rapid
Dry/ wet
Mass movement: rock fall
Mechanical weathering breaks up rock and they fall down slope.
Nature of movement: fall
Rate of movement: rapid
Dry
Erosion: Hydraulic action
Refers to the impact of the sheer force of the water itself ( without debris). This can exert enormous pressure upon a rock surface, thus weakening it. Such activity is sometimes know as wave pounding
Erosion: wave quarrying
A braking wave traps air as it hits a cliff face. The air is compressed into any gaps causing huge pressures. As the water retreats there is an explosive effect of the air pressure being released. This sealed the cliff face and allows storms to remove large chunks of it (can be known as cavitation)
Erosion: abrasion/ corrosion
Eroded material being thrown against the rock by the wave. Also conducts erosion of wave cut platforms due to movement of material back and forth
Erosion: attrition
Rocks which are carrying out abrasion are slowly worn down into smaller and rounder particles
Erosion: solution (corrosion)
Not overly common as sea water is generally alkaline rather than acidic. However, where seawater interacts with freshwater supplies carbon based rocks may be dissolved
