A level geography aqa - Coasts

Erosion

Processes by which rock, sand, and soil are broken down and carried away (i.e. weathering, glaciation)

Longshore drift

The movement of material along a coast by prevailing wind and waves (swash and backwash).

Sediment

Small pieces of rock and material broken down by erosion.

Deposition

The movement of sediment from one place to another, dropped off at the shore.

Transportation

The movement of eroded material

Saltation

Small pebbles and stones (sediment) are bounced along the river bed

What are the four types of erosion?

Abrasion, Attrition, Hydraulic action, Solution

Give an example of erosional landforms

Cracks, cave, arch, stack, stump, wave-cut platforms, etc

Give an example of depositional landforms

Spit, offshore bar, tombolo, etc

What is an input?

Material or energy moving into the system from outside

Give and example of an input in a coastal system?

Marine: energy from waves, tides, currents

Geological: rock type/structure

Atmospheric: precipitation, wind energy

Human: Land use, coastal protection

What is an output?

Material or energy moving out of the system

Give an example of an output in a coastal system?

Dissipation of wave energy, ocean currents, evaporation, erosional and depositional landforms

What is energy (in a coastal system)?

Driving force or power

What are stores/components?

The individual elements or parts of a system

What are flows/transfers?

The links or relationships between the components

What is a positive feedback loop?

A sequence of events that amplifies a change in the system promoting instability

What is a negative feedback loop?

A sequence of events that nullifies a change in the system promoting stability.

Define dynamic equilibrium

A balance between the inputs and outputs of a system

What is a landform?

A natural geographical feature that appears on the Earth's surface.

How are landforms created?

They are created and shaped by geographical forces such as tectonic movement and erosion.

What is a landscape?

An expanse of land that can be seen in a single view, it consists of geographical features that are characteristics of an area.

What is a wave?

A long body of water that forms when wind blows across the surface of the sea.

What three factors affect the size of a wave?

Wind speed

Wind duration

Fetch (distance over which the wind has blown)

What is an isobar map?

A map that shows different air pressures.

The closer the isobars are, the faster the wind speed.

What is the relationship between wind speed and air pressure?

Wind speed increases as air pressure decreases/becomes lower.

Why do high pressure areas have low wind speeds?

Air sinks and becomes compacted which reduces the formation of clouds and leads to light winds.

How do isobars indicate air pressure?

Isobars far apart represent high pressure

Isobars close together represent low pressure

What is the relationship between length of fetch and wave energy?

The longer the fetch is, the more wave energy waves gain. This is because the wind has blown over a long distance creating friction so the sea gains lots of energy.

What are the characteristics of a constructive wave?

Stronger swash than backwash

Low wave height

Shorter fetch

Less wave energy

Lower wave frequency (6-8/min)

What are the characteristics of a destructive wave?

Stronger backwash than swash

High wave height

Longer fetch

More wave energy

Higher wave frequency (10-14/min)

What is wave refraction?

The distortion of wave fronts as they approach an indented shoreline.

During wave refraction, why is there erosion at the headlands?

There is concentrated energy at headlands when waves refract causing erosion to take place as waves absorb the energy.

During wave refraction, why is there deposition at the beach/bay?

As the waves reach the bay they slow down and have less energy, the deposit sediment onto the beach because most of the wave energy has dissipated at the headlands.

What is a current?

Large masses of water moving in a specific direction from one location to another.

What are tides?

Changes in water levels of seas and oceans caused by the gravitational pull of the moon and sun

What is a sediment cell?

A stretch of coastline, usually bordered by two prominent headlands, where the movement of sediment is more or less contained/balanced.

Sediment Starvation

Give examples of sources of sediments at the coast.

Rivers

Cliff erosion

Longshore/littoral drift

Wind

Glaciers

Offshore

What is a sediment budget?

A balance between the loss and gain of sediment in a system via erosional and depositional processes.

Define dredging

Removal of sediment and debris from lakes, rivers and other bodies of water.

When might sediment be transferred outside the system?

When there is a severe storm which erodes the beach

What are geomorphological processes?

Processes which shape the land and create different landforms, can be both marine and sub-aerial.

What is aeolian transport?

Transport caused by the action of wind

Define weathering

The breaking down of rocks

What is mechanical weathering?

When rocks are broken down by physical processes (e.g. changes in temperature)

What is biological weathering?

The breakdown of rocks by plants and animals

What is chemical weathering?

The breakdown of rocks due to chemical reactions with rainwater

Define salt crystallisation

When salt crystals are deposited in cracks and the salt accumulates and applies pressure to the crack over time

What is wetting and drying?

Frequent cycles of rock rich in clay expanding when they get wet and contracting when they get dry causing the to crack and break apart

What is freeze-thaw weathering?

When water gets into cracks in the rock. The water freezes and expands, putting pressure on the rock. The ice then thaws releasing the pressure. Rocks eventually break apart into angular fragments as the process is repeated.

Give an example of biological weathering?

When plant roots grow in crack and break the rock up

When birds and animals dig burrows into cliffs

Define carbonation

The reaction of CO2 with rainwater to form weak carbonic acid which reacts with calcium carbonate in rocks to form calcium bicarbonate which is easily dissolved

Define oxidation

The reaction of rock minerals with oxygen to form rusty red powder leaving rock vulnerable to weathering

Define solution

The dissolving of rock minerals

Define mass movement

The downhill movement of material under the influence of gravity

What is a landslide?

The rapid movement of large blocks of rock downhill along a planar surface

What is a landslip/slump?

When blocks of rock become heavy due to saturation and slide rapidly along a curved surface

What is a mudflow?

The rapid movement of earth and mud flowing downhill, often after heavy rainfall.

What is runoff (mass movement)?

The rapid flow of water and sediment down a slope to enter the littoral zone

What is soil creep?

The slow movement of soil particles down a slope in response to gravity as the soil thaws

What is solifluction?

The slow movement of wet soil down a slope in cold periglacial environment

What is a rockfall (mass movement)?

The sudden collapse of rock fragments at a cliff face due to mechanical weathering or an earthquake

Define corrasion

Fragments of rock are picked up and hurled by the sea at a cliff. The rocks act like tools scraping and gouging to erode the rock

Define wave quarrying

The action of waves breaking against unconsolidated material such as sands and gravels.

Define swash-aligned beach

Beach found on irregular coastline in which waves arrive parallel to the shore, they experience minimal longshore drift.

Define drift-aligned beach

Beach in which waves approach the coast at angle.

Define hydraulic action

When air becomes trapped and compressed between the breaking wave and the cliff. The compressed air expands when the cliff retreats. This is a continuous process that forms cracks in the rock causing them to break off the cliff.

Define abrasion (erosion)

The 'sandpapering effect' as sediment is dragged up and down the shoreline, eroding and smoothing rocky surfaces.

Define solution

Weak acids in seawater dissolve alkaline rock (such as chalk or limestone).

Define attrition

Gradual wearing down of rock particles by impact and abrasion, as pieces of rock are moves by waves, tides and currents. Makes stones rounder and smoother.

List six factors that affect coastal erosion

Waves, rock type, presence of a beach, weathering, coastal management and geology.

Define abrasion (transportation)

The rolling of coarse sediment along the sea bed that is too heavy to be picked up and carried by the sea.

Define suspension

Smaller, lighter sediment is picked up and carried within the flow of the water.

Define solution (transportation)

Chemicals dissolved in the water, transported elsewhere.

Define saltation

Sediment 'bounced' along the seabed, light enough to be picked up or dislodged but too heavy to remain within the flow of the water.

How does rock type affect LSD?

The more easily eroded the rock, the greater the amount of sediment inputted into the system.

How does the type of wave affect LSD?

Type of wave determines where the smash or backwash is stronger therefore the deposition of sediment.

How does fetch affect LSD?

Fetch determines how much energy waves have therefore where sediment is eroded or deposited.

How does the shape of the coastline affect LSD?

Determines where energy is concentrated and dissipated , this influences where constructive waves form.

How does coastal management affect LSD?

Determines the amount of sediment built up on the coastline therefore the amount of sediment moved by LSD.

Describe the formation of a wave-cut notch

HA + A act at the base of the cliff due to low tidal range. Water enters rock and expands applying pressure at the base of the cliff causing it to break apart.

Describe the formation of a wave-cut platform

Notch increases and cliff collapses causing it to retreat. Concentrated energy around cliff causes corrasion, build up of close sediment at sea bed creates a sloping effect. Rock and sediment is further eroded via solution. A wave-cut platform forms.

Why does the rate of erosion of wave-cut platforms reduce over time?

As wave cut platform reaches further back into the cliff the wave can no longer ride the rock due to there being a low tide. This mean waves can't reach the unstable rock at the base so rates if erosion reduce.

Define strata

Layers of rock

Define bedding planes

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

Define joints

Vertical fractures caused by either contraction as sediment dries our, or by earth movements during uplift.

Define folds

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

Define 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.

Define dip

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

What is a beach?

Deposition landform extending from the highest high tide to the lowest low tide.

What is a storm ridge?

A ridge consisting of the largest material thrown up by the strong swash of larger waves in a storm period. Following tides cannot reach these features, so they remain untouched

What is a berm?

A terrace on a beach that has formed in the backshore, above the water level at high tide. Composed of small, well-rounded pebbles.

Describe the formation of a berm in the backshore zone.

Spring tides form a storm ridge. This is made when the largest material is known up the beach by the strong swash of larger waves. Following tides can't reach these structures so they remain untouched. Underneath the storm ridge there are a serious of smaller ridges (berms). These are formed when there are changes in the high tide mark.

Define cusps

Crescent-shaped indentations that form an beaches where there is a junction between sand and shingle.

Why do cusps form on the boundary of the backshore and foreshore?

The boundary is where shingle and sand meet. There is more shingle on the backshore due to the high and low tide bringing the shingle up the beach towards the cliff.

How does a cusp influence swash and backwash.

Sand is pulled of the beach by backwash, the indentation funnels water into the cusp. The shingle remains on the beach due to size and weight. The indentation becomes deeper due to the build-up of sediment on the edge.

What is an offshore bar?

Submerged ridges of sand created by waves offshore lying parallel to the coast.

Describe the formation of an offshore bar

Large, steep destructive waves plunge over the beach. The weak swash and strong backwash erodes material from the beach and deposits it off shore.

List the different zones on the beach.

Backshore, foreshore, nearshore and offshore.