Coastal Processes

Question 1

Abrasion

Answer 1

The process by which the coast is worn down by material carried by the waves. Waves throw these particles against the rock, sometimes at high velocity.

Question 2

Attrition

Answer 2

Material carried by the waves bump into each other and so are smoothed and broken down into smaller particles.

Question 3

Backwash

Answer 3

The motion of receding waves (water runs back down the beach).

Question 4

Corrosion

Answer 4

Chemical action of sea water. Acids in salt water slowly dissolve rocks on the coast. Limestone and chalk are particularly prone to this process.

Question 5

Hydraulic Action

Answer 5

This process involves the force of water against the coast. Waves enter cracks (faults) in the coastline and compress air within the crack. When the wave retreats, the air in the crack expands quickly causing a minor explosion (cavitation). This process is repeated continuously.

Question 6

Longshore Drift

Answer 6

Net effect of movement of sediment up and down the beach to the shore. Waves approach the beach at an angle in the same direction as prevailing winds and, as the waves advance, material is carried up the beach at an angle. Backwash pulls material down the beach at right angles to the shore under gravity. The process repeats along the shore.

Question 7

Saltation

Answer 7

The transport of hard particles over an uneven surface in a turbulent flow of air or water (bouncing across the seabed).

Question 8

Suspension

Answer 8

Fine light material is carried along in the water.

Question 9

Swash

Answer 9

When water is washed up the beach after an incoming wave has broken.

Question 10

Traction

Answer 10

Large boulders and rocks are rolled along the river bed.

Question 11

Coastal Recession

Answer 11

Another term for coastal erosion (the wearing away of land and the removal of beach or dune sediments by wave action, tidal currents, wave currents, drainage, or high winds)

Question 12

Dynamic Equilibrium (sediment cells)

Answer 12

State of balance between continuing processes, inputs, and outputs.

Question 13

Eustatic change

Answer 13

Sea level change due to an alteration in the volume of water in the ocean or a change in the geometry of the ocean basins which alters the volume of water they can hold. It is always a global effect.

Question 14

Isostatic change

Answer 14

Sea level change due to an alteration in the level of land, due to tectonic activity or the removal of great weight from the land (e.g. melting ice cap). It is a local effect.

Question 15

Plant succession

Answer 15

The changing of plant communities over time (the process of one plant community gradually or rapidly replacing another).

Question 16

Psammosere

Answer 16

Vegetation succession on sand dunes.

Question 17

Halosere

Answer 17

A succession in a saline environment e.g. salt marsh

Question 18

Thermal expansion (climate change)

Answer 18

The expansion of water as the temperature increases. Oceans absorb around 80% of the additional heat caused by emissions, resulting in a rise in sea level.

Question 19

Storm Surges (causes)

Answer 19

Changes in sea level caused by intense low-pressure systems- depressions and tropical cyclones- and high wind speeds. For every drop in air pressure of 10mb, the sea level rises by 10cm. Sea level rise is intensified in areas where the coastline is narrow/funnel-shaped, shallow or at times of high seasonal tides.

Question 20

Elliptical movement of waves

Answer 20

Wave transfers energy at right angles to the direction of its propagation.

Question 21

Sediment Cell

Answer 21

Coastal compartment which contains a complete cycle of sedimentation including sources, transport paths and sinks (movement of coarse sediment is largely self-contained).

Question 22

Sediment Cells (negative feedback)

Answer 22

Negative feedback is a stabilising mechanism acting to oppose changes to coastal morphology and establish equilibrium.

Question 23

Sediment Cells (positive feedback)

Answer 23

Positive feedback pushes a coastal system away from equilibrium by modifying its morphology until a threshold is reached, whereby a different type of response occurs.