8.1 Coastal processes (2)

Question 1

Freeze-thaw

Answer 1

Water seeps into cracks of cliff-face and freezes overnight.
When frozen, water expands by 9% widening and weakening the rock.

Question 2

Salt crystallisation

Answer 2

Saltwater gets into pores of rock, saline solutions get inside.
When saline solutions evaporate, salt crystals are left, as they accumulate over time they build up pressure expanding the rock

Question 3

Heating and Cooling

Answer 3

On coastlines with extreme temperature variations from day and night. (Namib desert North Namibia)
Rocks expand rapidly when hot and contract rapidly when cold, causing breaking apart of rock layers, outer layers peel off in exfoliation.

Question 4

Mass movement

Answer 4

Weathering processes weaken the rocks and expand the cracks.
Rain water lubricates the cracks and weakens the rocks by adding shear stress.
Cliffs made of hard rocks cause rockfalls.
Cliffs made of unconsolidated material (clay) lead to rotational slumping.

Question 5

Sediment cells

Answer 5

A simplified model that examines coastal processes and patterns in a given area.
Operates at a variety of scales from a single bay (Turtle bay Queensland) to a regional scale (South California coast).
Inputs and outputs are balanced.

Question 6

Longshore drift

Answer 6

The gradual movement of sediment along a coastline.
Swash moves in the direction of the prevailing wind, the backwash moves at a right angle to the beach, following the steepest gradient.

Question 7

Sediment source (Rivers)

Answer 7

Rivers - Fine-grained silts, clay and sands. Usually the largest source of coastal sediment.

Question 8

Sediment source (Cliffs)

Answer 8

Rock falls and slumps produce large amounts of material for beach building, (coarse sand and shingle)

Question 9

Sediment source (Sea)

Answer 9

Tides and constructive waves bring huge volumes of sand and clay deposited on the sea bed during the last Ice Age.

Question 10

Deposition

Answer 10

The sea dropping sediment (or material) is carried by the water at the coastline. When waves no longer have sufficient energy to continue to transport material

Question 11

Causes of coastal deposition

Answer 11

A significant change in the coastline. For example spits (Orford Ness in Suffolk)​.
Wave refraction around an island that is close to the coast can lead to the deposition of sediment between the island and the coast. ​