A-level Coasts terms

Abrasion

A form of erosion where loose material and sediment 'sandpapers' the walls and floors of the river, cliff or glacier. Also known as attrition.

Backshore

The upper beach closest to the land, including any cliffs or sand dunes.

Bar

A section of sand caused by deposition. They join two sides of a bay together, creating a lagoon behind it.

Beach Morphology

The surface shape of the beach.

Beach Nourishment

The addition of sand and sediment to an eroding beach by humans. The new material will be eroded by the sea which saves the cliffs or sand dunes from erosion and recession.

Coastal Recession

The retreat of a coastline due to erosion, sea-level rise or submergence.

Concordant Coast

A coastline where bands of alternate geology run parallel to the coast.

Corrasion

A form of mechanical erosion where material and sediment in the sea is flung at the cliff-face as waves break against it, this breaks up the rocks making up the cliff.

Corrosion

The weak acid in seawater and some types of seaweed react with particular rock minerals, causing erosion and weakening.

Dalmatian Coast

A concordant coastline with several river valleys running perpendicular to the coast. These valleys become flooded due to sea levels rising and produce long islands and inlets.

DEFRA's 1:1 Cost-Benefit Analysis

The evaluation of a coastal town's economic value compared to the cost of the management required.

Discordant Coast

A coastline where bands of alternate geology run perpendicular to the shore.

Dynamic Equilibrium

A system where its inputs and outputs are in balance. Short term changes can affect this balance, negative feedback loops help to take the system back to dynamic equilibrium.

Emergent Coast

A coastline that is advancing relative to the sea level at the time.

Estuary

The point at where the river meets an ocean, often muddy or silty. Sometimes estuaries become exposed at low tide or hazardous to traverse in a boat due to sandbanks

Eustatic

Global changes to sea levels. (change in sea level)

Long term sea level changes

• Sea level in the Pleistocene glacial were much lower than currently due to so much water being on the land in the form of ice.
• As ice melts - sea level rises. Estimated that sea levels have rise 120m since the end of the last ice age 10,000 years ago.

Fetch

The length of water over which the wind has travelled.

Fjord

Long narrow inlet of sea water which is between steep mountains. They are created when sea levels rise relative to the land, flooding coastal glacial valleys.

Foreshore

The lower part of the beach covered twice a day at high tide (the part of the beach that receives the most regular wave action).

Freeze Thaw (mechanical weathering)

A form of physical sub-aerial weathering where water freezes in the cracks of a rock, expands and enlarges the crack. This weakens the rock overtime leaving it more open to erosion.

Geology

The physical structure and arrangement of a rock.

Glacial Erosion

The removal of loose material by glacier ice, involving plucking, abrasion, crushing and basal meltwater. (necessary in the formation of Fjords).

Grading

The layering of sediments based on their size.

Groyne

A form of hard-engineering. Low-lying concrete or wooden walls, constructed perpendicular to the seafront and run out to sea. They encourage the trapping of sediment to reduce erosion caused by longshore drift or by winds.

Hard Management

The use of concrete structures to reduce or halt the recession of a coastline. Includes: Groynes, Sea Walls, Rock Armour.

High-energy Environment

A coast where wave action is predominantly large destructive waves, causing much erosion.

Hydraulic Action

The pressure of compressed air forced into cracks in a rock face will cause the rock to weaken and break apart.

Integrated Coastal Zone Management (ICZM)

Large sections of coastline (often sediment cells) are managed with one integrated strategy and management occurs between different political boundaries. It usually follows a holistic approach and takes into consideration different players.

Impermeable

A rock that does not allow water to pass through it.

Isostatic

A local change in sea level due to a change in local coastline or land height. (Change in land level)

• When ice is kilometres thick, its weight pushes the land down.
• Britain's north was glaciated and pushes down; southern areas were ice-free and tilted upwards slightly.
• When ice sheets melt at the end of an ice age, the land has been pushed down rebounds back upwards, Land tilted upwards starts ti sink back. This is called post-glacial adjustments.
• Sediments eroded from the sinking land will be redeposited on coasts (accretion)

Littoral Cell

An area of coastline which has all sediment processes occurring sources, transport and sinks. A littoral cell is not a closed system.

Longshore Drift

The transportation of sediment along a beach. Longshore Drift is determined by the direction of the prevailing wind.- When waves approach the beach at an angle of 30 degrees.

• Swash carries the beach sediment up the beach at the same angel as the waves approach.
• Backwash carries the sediment back the beach at a right angel to the shore, under the influence of gravity. = moves sediment along the coast.
• Predominant wind direction determines the direction of longshore drift.

Low-energy Environment

A coast where wave action is predominantly small constructive waves. Deposition usually takes place leading to beach accretion.

Mass Movement

Where there is a large downhill movement of material usually from a cliff-face.

• It is caused by gravity once a slope has become unstable: after waves have undercut resistant rocks or when rainwater enters unconsolidated rocks and forces particles apart.

Nearshore

The area before the shore where the wave steepness and breaks before they reach the shore and then reform before breaking on the beach. It extends from the low-tide zone and then out to sea.

Permeable

A rock that allows water to pass through it.

Plant Succession

Change to a plant community over time due to adaptation to changing growing conditions (eg. sand dunes and salt marshes).

Ria

Narrow winding inlet which is deepest at the mouth, formed when sea levels rise causing coastal valleys to flood.

Rock Armour

Large rocks or concrete blocks, used as barricades to reduce marine erosion at the base of cliffs.

Saltation

A form of transportation where smaller sediment bounces along the sea bed pushed by currents. This sediment is too heavy to be picked up by the flow of the water.

Salt Marsh

In sheltered bays or behind spits, salt and minerals will build up. Vegetation may establish, further stabilising the marsh.

Sand Dune

A depositional landform, where sand and sediment build up around driftwood and accumulate over time.

Sea Wall

A hard-management coastal defense, where a concrete wall is built parallel to the seafront, to redirect the energy of waves away from sensitive cliffs or the edge of a coastal town.

Sediment Cell

Sections of the coast bordered by prominent headlands. Within these sections, the movement of sediment is almost contained and the flows of sediment should act in dynamic equilibrium

• Has sources, transfers, and sinks
• erosion = source
• deposition = sink
• The amount of sediment gained and lost through sources and sinks can be calculated. = sediment budget.
• Good way to asses the extent of coastal change and evaluating coastal management strategies.

Sediment Budget

Use data of inputs, outputs, stores and transfers to assess the gains and losses of sediment within a sediment cell.

Shoreline Management Plan (SMP)

Identifies all of the activities, both natural and human, which occur within the coastline area of each sediment cell. They use this to recommend a combination of four actions for each stretch of that coastline:

• Hold the Line: Maintain existing and building of new defences.
• Advance the Line: Building new defences closer to the sea.
• Managed Realignment: Natural processes allowed to operate without interference, but carefully monitored.
• No Active Intervention: No investment in defences or maintenance of any existing defences.

Soft Management

The use of natural materials and environmentally sustainable approaches to reduce coastal recession. Includes: Beach Nourishment, Managed Retreat, Sand Dune Encouragement.

Subaerial Processes

The combination of mass movement and weathering that affects the coastal land above sea.

Submergent Coast

A coast that is sinking relative to the sea level of the time - isostatic sinking.

Till

Deposits of angular rock fragments in a finer medium.

Tombola

A spit joining mainland to an island.

Wave Quarrying

When air is trapped and compressed against a cliff which causes rock fragments to break off the cliff over time

Haff coasts

Consists of concordant features, long spits of sand and lagoons run parallel to the coast. Formed by flooding and deposition.

High energy coast

A coastline where strong, steady prevailing winds create high energy waves and the rate of erosion is greater than the rate of deposition.

low energy coasts

• typical landforms: beaches, spits

• coastlines where wave energy is low

• rate of deposition often exceeds rate of erosion of sediment

• e.g. many estuaries, inlets and sheltered bays. The Baltic sea, sheltered waters + low tidal range.

Wave-cut notch

a notch in a coastal cliff cut out by wave erosion

wave-cut platform

The smooth, level terrace sometimes found on erosional coasts that marks the submerged limit of rapid marine erosion.

cliff retreat

Cliffs move backwards due to erosion.

Cave-arch-stack-stump Sequence

• Hydraulic action and abrasion form caves that eventually meet in the middle to form a tunnel, above which is an arch
• Erosion and weathering make the arch more prominent.
• The arch collapses and only a stack is left
• Further wave erosion leaves a stump

Destructive waves

large waves that carry sand and other material away in the backwash

Constructive waves

A low wave that deposits material after it breaks, building up the beach. Swash is stronger than backwash.

long shore drift

The movement of water and sediment down a beach caused by waves coming in to shore at an angle

Weathering

The chemical and physical processes that break down rock at Earth's surface.

Talus scree slopes

Debree (talus) creates a slope at the foot of a cliff.

• Rock fragments fall to the base of the slope and form talus scree slopes
• They are steep, fan-shaped mounds of angular material.
• Large boulders at their core and smaller material on the top.
• Wave process work on the tallus scree - gradually reducing it in size until it can be transported away.

Mudflows

a rapid downhill movement of a mixture of water, rock, and soil

Block falls

occur on steep slopes as a cliff face is weathered, which loosens blocks and when wave erosion has created a wave cut notch so that a section of the cliff is no longer supported.

• rock sections or clumps slide to the base of the slope which may be covered with previous debri. as a result the cliff profile seems almost clear cut from where the rock has fallen.

sea walls

This is a type of hard engineering that involves the construction of a wall at the base of a retreating cliff or at the back of the beach. They often have a recurved face to deflect the waves back down the beach. They are durable and last a long time but are very ugly, so have to be buried under shingle.

Strata

layers of rock

Joints

(Vertical cracks) - These are fractures, caused either by contraction as sediment drys out, or by earth movement during uplift.

Bedding planes

Horizontal cracks; these are natural breaks in the strata, caused by gaps in time during periods of rock formation

Folds

Formed by pressure during tectonic activity, which makes rocks buckle and crumple.

Faults

Formed when the stress or pressure to which a rock is subjected, exceeds its internal strength (causing it to fracture). The faults then slip or move along fault planes.

Dip

This refers to the angle at which rock strata lie (horizontally, vertically dipping towards the sea, or dipping inland).

Lithology

The physical characteristics of particular rocks

The stabilising role of vegetation

plant roots bind the sediment together so they are less likely to erode
plant leaves slow down wind speeds at ground level, reducing erosion and increasing deposition
as plants lose leaves and die they add organic material to the sand

Berm

small ridges that coincide with high-tide lines and storm tides.

Characteristics of low energy coasts

• wave energy is low
• rate of deposition often exceeds rate of erosion of sediment
• short fetches
• gently sloping offshore zones
• landforms e.g. beaches, spits
• e.g. estuaries, inlets + sheltered bays

Characteristics of high energy coasts

• strong, steady prevailing winds = high energy waves
• long fetches
• steeply shelving offshore zones
• rate of erosion > rate of deposition
• landforms e.g. headlands, cliffs, wave cut platforms

Breaker zone

Area where waves approaching the coastline begin to break, usually where the water depth is 5-10m.

Surf zone

zone of breaking waves near shore

The coastal zone

• Lots of people live near the coats
• 1 billion people live on coasts that are at risk from flooding
• Half of the worlds population live within 200km of the coast
• Coasts represent a boundary where land and sea meet - terrestrial / marine processes interact.
• Experience extreme events, e.g. cyclones

Wavelength

The distance between two corresponding parts of a wave -either the wave trough or wave crest

Wave trough

Lowest point of a wave

Wave crest

Highest point of a wave

Wave height

the vertical distance from the crest of a wave to the trough

Swash

The movement of water up the beach after a wave breaks.

Backwash

The backward movement of water down a beach when a wave has broken

Swell waves

a relatively smooth ocean wave that travels some distance from the area of its generation.

Sand dunes

hills of sand shaped by the wind at the coast

The stages of sand dune succession

​- Embryo dunes form when seaweed driftwood or litter provides a barrier or shelter to trap sand.

• As the embryo grows, it is colonised by xerophytic pioneer plants, like sea couch grass, lyme grass, saltwort and sea rocket. the embryo dunes alter the conditions to something other plants can tolerate, allowing other plants to colonise and forms a fore dune
• Pioneer plants stabilise the sand allowing marram grass to colonise.
• Marram grass is marvellous because it:has waxy leaves to limit water loss through transpiration and resist wind-blown sand abrasion. has roots that can grow to 3m to reach down the water table and the stem can grow 1m a year to avoid burial by deposited sand. allows the dune to grow, rapidly forming a yellow dune. it's called this because the surface is mainly sand, not soil
• As the marram grass and sedge grass dies, it adds hummus to the sand, creating soil. A grey dune develops, with plants such as gorse. grey dunes and dune slacks are fixed
  dunes examples of plants are: red fescue, heather, creeping willow
• The dune is now above high tide level, so rain washes salt from the soil, making it less saline.
• The soil now has improved nutrients and moisture retention, allowing non-xerophytic plants to colonise the dunes until a climax plant community is reached, in equilibrium with the climate and soil conditions. e.g. bramble, pine, birch

Sand dune formations

• Embryo Dune - above the berm (High tide)
• Fore dune
• Yellow dune
• Grey dune /Mature dunes - May also get a dune slack
• Eventually a woodland

Sedimentary rock

A type of rock that forms when particles from other rocks or the remains of plants and animals are pressed and cemented together - most easily eroded - erosion rate of 2.5cm annually on average.

Igneous rock

a type of rock that forms from the cooling of molten rock at or below the surface - most resistant from erosion - erosion rate of 1mm annually on average.

Metamorphic rock

A type of rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions. - Made up of sedimentary rock and igneous rocks that have been subjected to heat. - More resistant than sedimentary but not as resistant as igneous.

Halophytes

plants that live in highly saline (salty) soil (embryo dunes, fore dunes especially)

Xerophytes

plants with adaptations that enable them to survive in dry habitats or habitats where water is in short supply in the environment. - Grey dunes.

Biological weathering

any weathering that's caused by the activities of living organisms.

Chemical weathering

the process by which rocks break down as a result of chemical reactions

Mechanical weathering

The type of weathering in which rock is physically broken into smaller pieces

Sub-aerial weathering

Top of cliffs being attacked by the weather (wind, rain, heat, cold etc.), weakening it.