COASTS

Question 1

Spit

Answer 1

Sand or shingle beach ridge extending beyond a turn in the coastline. usually greater than 30 degrees. At turn, the longshore drift current spreads out and loses energy leading to deposition. The length of a spit is determined by the existence of secondary currents causing erosion, either the flow of a river or wave action which limits its length

Question 2

Bayhead Beach

Answer 2

• A awash aligned feature, where waves break at 90 degrees to the shoreline and move sediment into the bay, where a beach forms. Due to wave refraction, erosion is concentrated at headlands and the bay is an area of deposition

Question 3

Tombolo

Answer 3

A sand or shingle bar that attaches the coastline to an offshore island. Tombolos form due to wave refraction around an offshore island which creates an area of calm water and deposition between the island and the coast. Opposing longshore currents may play a role, in which case the depositional feature is similar to a spit.

Question 4

Barrier beach/bar

Answer 4

A sand or shingle beach connecting two areas of land with a shallow water lagoon behind. These features occur when a spit grows so long that it extends across a bay, closing it off.

Question 5

Hooked/Recurved Spit

Answer 5

A spit whose end is curved landward, into a bay or inlet. The seaward end of the spit naturally curves landward into shallower water. The ‘hook’ may be made more pronounced by waves from a secondary direction to the prevailing wind

Question 6

Offshore bar

Answer 6

A ridge of sand found offshore - can be submerged during high initially formed by riptide currents following destructive waves

Question 7

mass movement processes

Answer 7

Landslide, Rotational slumping, slide, rock fall, topple, mudslides, slumping

Question 8

weathering

Answer 8

mechanical, chemical, biological

Question 9

Perculation

Answer 9

the movement of water through soil

Question 10

Flocculation

Answer 10

when sediment is dropped, such as clays and polymers, they clump together

Question 11

Sub Aerial Process

Answer 11

land-based processes which alter the shape of the coastline. These are a combination of weathering and mass movement.

Question 12

Mechanical (physical) weathering

Answer 12

Mechanical or physical weathering is the fracture and breakdown of rocks into fragments. Freeze-thaw and Salt crystallisation

Question 13

salt crystallisation

Answer 13

This is when salt crystals are deposited in cracks and over time the salt accumulates and applies pressure to the crack (similar to freeze-thaw weathering).

Question 14

Chemical weathering

Answer 14

decomposition of rocks (literally, changing the minerals)

Question 15

Soil Creep

Answer 15

Soil creep is a slow but continuous process. It typically occurs on most slopes over 5 degrees. Soil creep rarely exceeds speeds of 1cm per year. Creep occurs as the result of repeated expansion and contraction of material. Cycles of freeze-thaw heave particles upon freezing and allow them to fall further downslope when the ice melts. Alternating hydration and dehydration have the same effect.

Question 16

Slump

Answer 16

Rainwater infiltrates the cliff through unconsolidated, porous material (e.g. boulder clay). This then creates a slip plane. The weight of the saturated clay causes the material to slump along the slip plane.

Question 17

rock fall

Answer 17

They are most commonly triggered by undercutting in the inter-tidal zone or freeze-thaw weathering.

Question 18

Mudflows

Answer 18

A mudflow is an earthflow consisting of material that is wet enough to flow rapidly and that contains at least 50 percent sand, silt, and clay-sized particles.

Question 19

Soil creep

Answer 19

Soil creep is a slow but continuous process. It typically occurs on most slopes over 5 degrees. Soil creep rarely exceeds speeds of 1cm per year. Creep occurs as the result of repeated expansion and contraction of material.

Question 20

Land slide

Answer 20

This is the downslope movement of a large block of material that moves as a coherent mass. This means it retains its internal structure until hitting the base of the slope and fracturing into smaller pieces. It is more common over wet periods, on steep slopes and often occurs on coastlines.

Question 21

Marine Processes

Answer 21

Marine processes are those associated with the action of waves. This includes erosion, transportation and deposition.

Question 22

Erosion

Answer 22

Erosion refers to the wearing away of the land surface and removal of materials by river and seawater, ice and wind. There are four main processes of erosion along the coast. These are hydraulic action, abrasion and corrasion, attrition and solution.

Question 23

Hydraulic Action

Answer 23

Waves breaking at the foot of a cliff force air in cracks to be compressed. Loose rocks are dislodged and removed. When the wave retreats the compressed air rushes out of the crack and can further weaken faults in the cliff face.

Question 24

Abrasion

Answer 24

Abrasion is the sandpaper effect of loose rocks being scraped along bare rock. It often smooths and polishes the rock.

Question 25

Attrition

Answer 25

Attrition is when rocks carried by seawater collide – gradually making them smaller and smoother.

Question 26

Transportation

Answer 26

Transportation is the movement of sediment by the action of waves.

Question 27

Traction

Answer 27

Traction involves the rolling of large and heavy rocks along the seabed.

Question 28

Saltation

Answer 28

Saltation involves smaller material being bounced along the seabed. The video below shows material being bounced along a beach by waves.

Question 29

Suspension

Answer 29

Suspension is when lighter sediment is suspended within the water. This often discolours the water close to the shore.

Question 30

Solution

Answer 30

Sediment that has dissolved completely will be transported in solution.

Question 31

Deposition

Answer 31

Deposition occurs when energy levels decrease in environments such as bays and estuaries. Where deposition occurs on the inside of a spit a salt marsh can form.

Question 32

Corrosion

Answer 32

the process of chemicals eroding away rocks