coasts

What are the four main components of a coastal system?

Inputs, outputs, flows (transfers), and stores (components).

Define dynamic equilibrium in a coastal system.

A state of balance between the inputs and outputs of a system.

How does negative feedback function in a coastal system?

It counteracts change, returning the system to its original state, such as when eroded beach sediment is deposited to grow the beach back.

What is positive feedback in a coastal system?

It amplifies change, moving the system further away from its original state, such as a groyne trapping sediment and depriving areas down-drift.

What creates wind in the coastal environment?

Air moving from areas of high pressure to areas of low pressure.

How do tides affect coastal landforms?

They determine where waves break; most landforms are created or destroyed in the area between the maximum high tide and minimum low tide.

What is the difference between spring and neap tides?

Spring tides have a large tidal range (higher high tides, lower low tides) when the Sun, Moon, and Earth align; neap tides have a small tidal range when they are at right angles.

Describe the formation of a rip current.

Plunging waves build up water at the beach; this water meets resistance from incoming waves and is forced back below the surface through gaps in sandbanks.

What three factors determine wave size and energy?

Wind speed, duration, and fetch.

What are the characteristics of constructive waves?

Low frequency, low and long shape, powerful swash, and weak backwash, leading to sediment deposition.

What are the characteristics of destructive waves?

High frequency, high and steep shape, strong backwash, and weak swash, leading to sediment removal.

What defines a high energy coast?

Coasts receiving high inputs of energy from powerful waves, often characterized by sandy coves, cliffs, and higher rates of erosion than deposition.

What defines a low energy coast?

Coasts receiving low energy inputs, often characterized by saltmarshes, mudflats, and higher rates of deposition than erosion.

What is a sediment budget?

The difference between the amount of sediment entering a coastal system and the amount leaving it.

What occurs when a coastal system has a positive sediment budget?

More sediment enters than leaves, resulting in the building of the coastline.

What is a sediment cell?

A self-contained length of coastline where sediment movement is contained, acting as a closed system.

Define corrasion (abrasion) as an erosional process.

Bits of rock and sediment transported by waves smash and grind against cliffs, breaking off pieces and smoothing surfaces.

What is hydraulic action?

The process where air in cracks in cliffs is compressed by crashing waves, exerting pressure that breaks off rock.

Explain the process of cavitation.

As waves recede, compressed air in cliff cracks expands violently, exerting pressure that breaks off rock pieces.

What is wave quarrying?

The energy of a breaking wave is sufficient to detach bits of rock from a cliff face.

Define solution (corrosion) in coastal erosion.

The process where soluble rocks like limestone or chalk are gradually dissolved by seawater.

What is attrition?

The process where bits of rock in the water smash against each other, breaking into smaller, smoother pieces.

Distinguish between suspension and saltation in sediment transport.

Suspension carries very fine material like silt and clay via turbulence, while saltation moves larger particles like pebbles and gravel that are too heavy for suspension.

What is traction in the context of coastal transport?

The process where very large particles, such as boulders, are pushed along the seabed by the force of water.

How does longshore drift move sediment along a coastline?

Swash carries sediment up the beach at an angle, while backwash carries it back down at right angles to the shoreline, resulting in a net movement of sediment along the coast.

What is the primary difference between marine and aeolian deposition?

Marine deposition involves sediment carried and dropped by seawater, whereas aeolian deposition involves sediment carried and dropped by wind.

Under what conditions does deposition occur?

Deposition occurs when the sediment load exceeds the ability of the water or wind to carry it, often due to an increase in load or a decrease in energy/speed.

How do friction and turbulence affect the speed of wind or water flow?

Friction increases when waves enter shallow water or wind reaches land, and turbulence occurs when flow encounters obstacles; both processes slow the flow, leading to deposition.

What is sub-aerial weathering?

The gradual breakdown of rock by agents such as ice, plant roots, and acid, which weakens cliffs and makes them more vulnerable to erosion.

Explain the process of salt weathering.

Saline water enters cracks at high tide; as the tide recedes, water evaporates, leaving salt crystals that expand and exert pressure on the rock, causing fragments to break off.

What is freeze-thaw weathering?

A process occurring in areas with fluctuating temperatures where water enters cracks, freezes, expands, and eventually weakens the rock, causing it to shatter.

How does chemical weathering affect rocks containing calcium carbonate?

CO2 in the atmosphere dissolves in rainwater to form weak carbonic acid, which reacts with calcium carbonate to gradually dissolve the rock.

What is mass movement in a coastal environment?

The shifting of material downhill due to gravity, often triggered when cliffs are undercut by wave action, creating an unstable overhang.

What distinguishes a landslide from a slump?

A landslide involves material shifting in a straight line, whereas a slump involves material shifting with a rotation, often leaving a curved indented surface.

What are the primary triggers for mudflows?

Heavy rain saturates steep slopes, increasing water pressure within the rocks and causing the material to flow downslope.

Why are unconsolidated rocks like clay particularly prone to collapse?

There is little friction between particles, and heavy rain can saturate the material, further reducing friction and increasing the likelihood of slope failure.

How do wave-cut platforms form?

Wave erosion creates a notch at the high-water mark; the rock above becomes unstable and collapses, leaving behind a flat surface known as a wave-cut platform.

How do headlands and bays form?

They form where bands of alternating hard and soft rock exist at right angles to the shoreline; soft rock is eroded quickly to form bays, while hard rock remains as headlands.

What is the sequence of formation for caves, arches, and stacks?

Weak joints in a headland are eroded into caves; caves on opposite sides of a headland join to form an arch; when the arch collapses, it leaves a stack.

What is the difference between shingle beaches and sand beaches?

Shingle beaches are steep and narrow with larger particles, while sand beaches are wide and flat with smaller particles.

What are runnels and cusps on a beach?

Runnels are grooves in the sand running parallel to the shore, and cusps are crescent-shaped indentations formed on beaches of mixed sand and shingle.

How does a spit form?

Longshore drift continues to deposit material across a river mouth or where the coast changes direction, creating a bank of sand and shingle extending into the sea.

What is the difference between a simple spit and a compound spit?

A simple spit is a straight feature, while a compound spit has multiple recurved ends caused by changing wind and wave directions over time.

How do offshore bars and tombolos differ?

An offshore bar forms when material is deposited off the coast and remains partly submerged, while a tombolo is a bar that connects the shore to an island.

What are barrier beaches?

Long, narrow islands of sand or gravel that run parallel to the shore and are detached from it, often forming in areas with powerful waves and gentle offshore slopes.

How do sand dunes develop?

Sand deposited by longshore drift is moved by wind, trapped by obstacles like driftwood, and stabilized by vegetation like marram grass, forming embryo dunes that migrate inland.

What role does vegetation play in sand dune formation?

Vegetation stabilizes the sand and encourages further accumulation, allowing the dunes to grow and eventually migrate inland.

How do saltmarshes form in sheltered environments?

Mud and silt are deposited in low-energy environments, colonised by salt-tolerant vegetation which traps more sediment, gradually building the land upwards.

What is the difference between eustatic and isostatic sea level change?

Eustatic change is caused by a change in the volume of water or ocean basins (global), while isostatic change is caused by vertical movements of the land (local).

How do climate changes affect eustatic sea levels?

Temperature increases cause ice sheet melting and thermal expansion of water, raising sea levels; temperature decreases store water in glaciers, lowering sea levels.

What is the primary cause of isostatic land movement related to ice sheets?

The accumulation of ice sheets causes crustal depression, while the removal of ice weight causes slow post-glacial uplift.

What is the current trend in global sea level rise?

Since approximately 1930, sea levels have been rising, currently at a rate of about 2mm per year.

What are the predicted impacts of a 0.5m sea level rise on the Maldives?

The Maldives would be submerged.

What is a 'coastline of emergence'?

A coastline formed by sea level fall, characterized by raised beaches and relict cliffs no longer reached by the sea.

What are the defining characteristics of a Fjord?

A drowned glacial valley that is straight, narrow, steep-sided, and deep inland, with a shallow threshold at the mouth.

How is a Dalmatian coastline formed?

It is formed when valleys lying parallel to the coast are flooded, leaving islands parallel to the coastline.

What is a 'relict' landform?

A landform created by processes from a different period of sea level or climate that may still be subject to modern coastal processes.

What is the purpose of a cost-benefit analysis in coastal management?

To determine which coastal areas are defended based on available funding, typically prioritizing large settlements and important industrial sites.

Define the 'Hold the line' management strategy.

Maintaining existing coastal defences.

Define the 'Managed realignment' management strategy.

Allowing the shoreline to move while managing the retreat to minimize damage.

What is the primary disadvantage of using a sea wall?

It creates a strong backwash that can erode the material beneath the wall.

How do groynes function to protect the coast?

They are built at right angles to the coast to trap sediment transported by longshore drift, creating wider beaches that absorb wave energy.

What is the main disadvantage of groynes?

They starve down-drift beaches of sand, leading to increased erosion and flooding in those areas.

What is the primary advantage of beach nourishment?

It is a natural method that effectively absorbs wave energy.

What is the main disadvantage of marsh creation?

It is only effective in low-energy coastal environments.

What is a Shoreline Management Plan (SMP)?

A plan devised for each sediment cell that coordinates local authorities to manage coastal areas through specific strategies like holding or retreating the line.

What is Integrated Coastal Zone Management (ICZM)?

A dynamic strategy that considers all elements of the coastal system—including land, water, people, and the economy—to manage the coast as a whole.

Why is hard engineering often considered less sustainable than soft engineering?

Hard engineering is expensive, disrupts natural processes, and often has a higher negative environmental impact.

What causes the formation of channels in mudflats?

Erosion by tidal currents or streams.

What is the effect of groundwater abstraction on land level?

It causes land subsidence due to the shrinkage of drained marshland.

How does sea floor spreading affect sea level?

It increases the volume of the ocean basin, which leads to a decrease in sea level.

What is a Rias coastline?

A coastline formed where river valleys are partially submerged, resulting in a gentle long and cross-profile.

What is the main advantage of dune regeneration?

It is a natural and sustainable method of providing a barrier against flooding and erosion.

How does coastal realignment work?

By breaching existing defences and allowing the sea to flood the land, which eventually develops into a marshland.