Coasts. A Level. 4 Marker

Question 1

Outline the processes which lead to the development of barrier beaches (2018)

Answer 1

A barrier beach is usually formed as an extension to a spit. Longshore drift moves sediment along the coastline until there is a change in coastline. A spit develops, usually in a bay and once the spit develops across the whole bay, a barrier beach is formed. it is unlikely to form in estuaries as the force of the river current will always keep part of the estuary clear. Colonization by vegetation can stabilize the barrier beach and trap further sediment keeping the barrier beach above sea even at high tide.

Question 2

Explain the development of salt marsh environment (2019)

Answer 2

Salt marshes tend to develop in sheltered estuaries behind spits. As the spit develops, the area behind it becomes sheltered. Silt is deposited by the river which gradually builds up to form an intertidal mud flat. The mud flat continues to build and rise above sea level with the addition of further silt. Holosere colonization takes place, as holophytes, vegetation which is highly adapted to environment colonists the mud which itself traps further sediment.

Question 3

Outline the process of sub-aerial weathering in the development of coastal landscapes. (2020)

Answer 3

Sub-aerial weathering are processes that slowly break down coastline, weaken the underlying rocks and allow sudden movements or erosion to happen more easily. Examples of subaerial weathering include mechanical (physical), biological and chemical weathering.
For example chemical weathering occurs when weak carbonic acid in rainwater attacks limestone cliffs. This leads to the formation of karst environment.
Biological weathering refers to the processes that lead to the breakdown of rocks by the action of vegetation and coastal organisms. For instance, seaweed attaches itself to rocks and the action of the sea can be enough to cause swaying seaweed to pride away loose rock from the sea floor.

Question 4

Outline the role of waves in the transportation of sediments at the coast (2021)

Answer 4

Constructive waves tend to bring sediment to the beach. This is due to the low energy nature of these wave. They tend to have low frequency,height and limited backwash. The swash os therefore a key factor in bringing sediment onshore.
On contrary, destructive waves tend to remove sediments from beaches and coastlines. They have higher frequency, greater wave height and powerful backwash that is instrumental in transporting material back out to sea.

Question 5

Explain the concept of the sediment cell (specimen)

Answer 5

A sediment cell is a closed system usually bounded by headlands or a change in longshore drift. Within a sediment cell, there is erosion, transport and deposition of sediment within a long term cycle. The only inputs into the sediment come from erosion from the sea bed or land. There is little or no movement of sediment between cells. Human activity such as beach management can interrupt the natural system bringing it to disequilibrium within the cell leaving some areas at risk of erosion.