[Time to do another one of these, on a different topic. Note this essay is in the style of the exam board OCR. It is a synoptic essay - linking coastal landforms to climate change. This topic matter is also relevant to other exam boards (though with a smaller mark allocation).]
A reminder: for A level Geography, there are two key Assessment Objectives (AOs):
AO1: demonstrate knowledge and understanding of places, environments, concepts, processes, interactions, and change, at a variety of scales.
AO2: apply knowledge and understanding in different contexts to interpret, analyse, and evaluate geographical information and issues.
So, as on previous occasions, here are two versions of the answer.
The first answer is unannotated.
The second answer is in two formats:
(a) AO1 in italics
(b) AO2 in bold.
[Note the self-imposed word limit of 800 words for this mark allocation]
Assess the importance of climate change in influencing coastal landforms. (33 marks)
Climate change in the past, present and future impacts on sea levels. Changes in sea level resulting from changes in the volume of water in the global oceans are known as eustatic changes. These changes are due to changes in global temperatures. These can affect both the amount of water in the oceans and its density. An increase in global temperature leads to higher rates of melting of ice stored on the land in ice sheets, ice caps and valley glaciers. Consequently, there is a global increase in the volume of water in the ocean and a rise in sea level. Also, when temperatures rise, water molecules expand, and this also leads to them occupying an increased volume.
At the end of the last glacial period, which happened about 10,000 years ago, temperatures were about 9°C lower than they are today and sea level was about 90 m lower than it is now. When the sea level rose, it formed several submerged or flooded landforms.
One landform is a ria, which is a drowned river valley. The lowest part of the river’s course and the floodplains by the river get completely flooded. In cross section rias have an open V-shape with the valley sides quite gently sloping. In long profile the depth reduces inland. When seen from above they tend to be winding, showing the original route of the river and its valley. There are many rias on the south coasts of Devon and Cornwall, for example at Salcombe and Fowey.
Another landform is fjords. Fjords are submerged glacial valleys. They have steep valley sides, and the water is very deep. The have a U-shaped cross section because this was the original shape of the glacial valley. They also tend to be much straighter than rias as the glacier would have truncated any interlocking spurs when it moved through the valley. The Sogne Fjord in Norway is 200 km long and over 1000 m deep.
Another landform created by rising sea level is a shingle beach. As sea level rose at the end of the last glacial period, wave action pushed marine sediments onshore, forming tombolos and bars. The tombolo at Chesil Beach was formed during the Flandrian Transgression. Sediment carried into the English Channel by meltwater during the glacial period built up in Lyme Bay.
As sea level rose at the end of the glacial period, due to warming, the sediment was carried onshore by the south-westerly prevailing winds and waves. It moved until becoming attached to the Isle of Portland at one end and the mainland at Abbotsbury at the other.
All these landforms are also affected by processes going on at present-day sea level and could also change in the future. Both rias and fjords may be altered by the waves acting on their sides and eroding them. The valley sides may also be changed by the subaerial processes in today’s climate or in any different warmer climate conditions of the future. This might lead to reduced steepness of the valley sides.
With sea levels predicted to rise by a further 0.6 m in the next 100 years, water depth in rias and fjords will increase. Marine erosion is also likely to increase due to stormier conditions and larger waves. Shingle beaches, being made of loose sediment, are especially at risk of modification.
A raised beach is a coastal landform that is found sitting above an active beach and coastline. They are often 2 or 3 metres above current sea level and are flat platforms or benches in the landscape. Sometimes they have a fossil/inactive cliff at the back. During the onset of glacial periods, such as the Devensian, sea levels fell as water was locked up in ice meaning the sea withdrew from active beaches, eventually stranding them above lowered sea levels. Sea levels fell 100–120m in the last glacial period.
Climate drives sea-level change, which can create raised beaches, as shown above. But, in many places, isostatic changes in land levels also play a role. In Scotland and Scandinavia most raised beaches have formed in the last few thousand years as land has rebounded upwards in response to the removal of the weight of ice sheets. Climate change today is causing sea levels to rise due to land-based ice melt and thermal expansion. Sea levels could rise by 1–2m by 2200 at current rates. This could drown existing beaches and potentially reactivate ancient, raised beaches in some places.
In conclusion, coastal landforms are influenced by sea level rises that have occurred in the past which has formed and developed some distinctive landforms such as rias, fjords and shingle beaches. Sea levels are still rising now and will keep rising in the future and so the processes will continue. (795)
Assess the importance of climate change in influencing coastal landforms. (33 marks)
Climate change in the past, present and future impacts on sea levels. Changes in sea level resulting from changes in the volume of water in the global oceans are known as eustatic changes. These changes are due to changes in global temperatures. These can affect both the amount of water in the oceans and its density. An increase in global temperature leads to higher rates of melting of ice stored on the land in ice sheets, ice caps and valley glaciers. Consequently, there is a global increase in the volume of water in the ocean and a rise in sea level. Also, when temperatures rise, water molecules expand, and this also leads to them occupying an increased volume.
At the end of the last glacial period, which happened about 10,000 years ago, temperatures were about 9°C lower than they are today and sea level was about 90 m lower than it is now. When the sea level rose, it formed several submerged or flooded landforms.
One landform is a ria, which is a drowned river valley. The lowest part of the river’s course and the floodplains by the river get completely flooded. In cross section rias have an open V-shape with the valley sides quite gently sloping. In long profile the depth reduces inland. When seen from above they tend to be winding, showing the original route of the river and its valley. There are many rias on the south coasts of Devon and Cornwall, for example at Salcombe and Fowey.
Another landform is fjords. Fjords are submerged glacial valleys. They have steep valley sides, and the water is very deep. The have a U-shaped cross section because this was the original shape of the glacial valley. They also tend to be much straighter than rias as the glacier would have truncated any interlocking spurs when it moved through the valley. The Sogne Fjord in Norway is 200 km long and over 1000 m deep.
Another landform created by rising sea level is a shingle beach. As sea level rose at the end of the last glacial period, wave action pushed marine sediments onshore, forming tombolos and bars. The tombolo at Chesil Beach was formed during the Flandrian Transgression. Sediment carried into the English Channel by meltwater during the glacial period built up in Lyme Bay.
As sea level rose at the end of the glacial period, due to warming, the sediment was carried onshore by the south-westerly prevailing winds and waves. It moved until becoming attached to the Isle of Portland at one end and the mainland at Abbotsbury at the other.
All these landforms are also affected by processes going on at present-day sea level and could also change in the future. Both rias and fjords may be altered by the waves acting on their sides and eroding them. The valley sides may also be changed by the subaerial processes in today’s climate or in any different warmer climate conditions of the future. This might lead to reduced steepness of the valley sides.
With sea levels predicted to rise by a further 0.6 m in the next 100 years, water depth in rias and fjords will increase. Marine erosion is also likely to increase due to stormier conditions and larger waves. Shingle beaches, being made of loose sediment, are especially at risk of modification.
A raised beach is a coastal landform that is found sitting above an active beach and coastline. They are often 2 or 3 metres above current sea level and are flat platforms or benches in the landscape. Sometimes they have a fossil/inactive cliff at the back. During the onset of glacial periods, such as the Devensian, sea levels fell as water was locked up in ice meaning the sea withdrew from active beaches, eventually stranding them above lowered sea levels. Sea levels fell 100–120m in the last glacial period.
Climate drives sea-level change, which can create raised beaches, as shown above. But, in many places, isostatic changes in land levels also play a role. In Scotland and Scandinavia most raised beaches have formed in the last few thousand years as land has rebounded upwards in response to the removal of the weight of ice sheets. Climate change today is causing sea levels to rise due to land-based ice melt and thermal expansion. Sea levels could rise by 1–2m by 2200 at current rates. This could drown existing beaches and potentially reactivate ancient, raised beaches in some places.
In conclusion, coastal landforms are influenced by sea level rises that have occurred in the past which has formed and developed some distinctive landforms such as rias, fjords and shingle beaches. Sea levels are still rising now and will keep rising in the future and so the processes will continue. (795)