Examine the Factors That Affect the Formation of Erosional and Depositional Landforms

Examine the factors that affect the formation of erosional and depositional landforms

Erosional landforms are the feature of the four main processes of erosion and include cliffs, stacks, stumps and bays. Depositional landforms are those that have been formed by the accumulation of deposited sediment such as beaches and spits. There are many factors that the formation of coastal landforms but primarily are the different rock types, structure and wave action. Looking at some landforms such as Sandy Hirst spit and the landforms at Torness and Skateraw it is possible to see how some of these factors come into effect.

The Sandy Hirst spit at Tyninghame is a prime example of a depositional landform. The spit has formed by a number of depositional processes. A prevailing offshore wind has caused longshore drift to move sediment along the coastline via constructive waves until it has reached the Tyne Mouth. Here, the beach material has continued to stretch out over the estuary and has created a spit. Due to the strong flow of the river, the spit has been unable to close up the estuary to create a bar. Also, due to a secondary wind hitting the spit, a re-curved end has formed. On the inland side of the spit a large salt marsh has been created due to the fact that the area has been sheltered from the tide and the water has stagnated. Sandy Hirst is rarely breached due to the large amounts of vegetation, such as Marram Grass which keeps the sand together and stable; and also, because of the amount of humus, the trees on the head of the spit.

At Torness and Skateraw, there is a raised beach on the western side of the bay. Raised beaches are often caused by isostatic change in the sea level, but at Torness the feature has been created by eustatic rebound in the land. In the last ice age around 25,000 years ago, the area (and the majority of Scotland) was covered in over 1km of ice; this placed the land under a huge amount of pressure; squeezing the land downwards. Now that the ice is gone, the land is now continuing to rise up and Scotland in fact has one of the fastest rates of rebound in the world. Due to this, we are now able to see the raised beach that Chapel Point is situated on. Also around the bay at Torness there is a limestone base with several small glacial erratic. These glacial deposits can also be observed in the slumping clay cliffs on the east side of the bay that display an unconsolidated un-stratisfied clay matrix – small pieces of different types of rock have been picked up by a glacier and deposited in the clay and this is why they are there now.

The Gegan in East Lothian is a stack; a feature of erosion. There are a few factors that affect the formation of a stack – one of these being rock type. The rocks at Seacliff are primarily red sandstone, which is a soft rock that is less resistant to erosion, so this means that it is more easily broken down and these features form. Stacks are the remnants of other coastal features. Firstly, the sea will erode weaknesses in the rock to form a cave, and when the cave has eroded fully through, an arch will be formed. The rock on each base of the arch will continue to be eroded by the sea until finally the weight of the heavy arch platform can no longer be sustained by the bases, and the centre collapses; leaving a stack. The Gegan may go on to further erode and collapse into the sea, causing a stump. The wave action is also a factor in the erosion of the stack – processes such as Hydraulic action mean that wave water is