KQ3-Submergent landforms Flashcards
why does sea level rise when global temperatures increase?
meltwater from ice sheets, glaciers and ice caps leads to a transfer of water to the global ocean store, so a consequent rise in sea level
1 (degree Celsius) rise in temperature leads to a sea level rise of
2m
what is the Flandarian transgression?
At the end of the Wurm glacial period, 25K years ago, temperatures were 9 (degree Celsius) lower than today and sea level was 90m lower. Since then ice has melted and this period of significant rise in sea level sis known as the Flandarian transgression
What are Rias and how do they form?
Submerged river valleys, formed as sea levels rise
How does drainage change across course of the river valley?
lowest part of the valley, i.e. floodplains may become completely drowned and the upper part and middle may remain exposed
In long section, Rias exhibit…
a smooth profile and water of uniform depth
In plan view, Rias exhibit …
a dendritic profile, formed by fluvial erosion in the channel and sub-aerial processes at the valley sides
Name one Ria in the UK, when was this formed?
One at Salcombe, Kingsbridge Estuary, considered to have formed during Flandarian Transgression
Describe the cross section of a Ria
Gently sloping on the sides, wit relatively shallow water becoming increasingly deep towards the centre
Describe the profile of the Ria at Salcombe
- Remained relatively deep
- Shallow entrance (or threshold) due to the deposition of a sand bar at the entrance of the low energy environment at mouth
Describe what happened to Rias during Flandarian Transgression (hint: deposition)
typically underlain by alluvial deposits, eroded by rivers that flowed during the Pleistocene glacial period. During interglacial period, further deposition would of occurred due to less surplus energy. Therefor during the Flandarian Transgression, significant infilling of river channels would of occurred
what are fjords?
submerged glacial valleys
Describe the cross section of fjords
steep valley sides and very deep, often reaching 1000m
How long is the Sogne fjord in Norway?
200km
why is the basin shallower at the end? give an example.
due to lower rates of erosion at the seaward end, where the ice thinned in warmer conditions. Example is Milford sound, they also have straighter planforms as the glacier truncates any interlocking spurs
Have rates of erosion changed in Fjord since Flandarian Transgression?
they have remained high due to the depth of water e.g. west of south island cost where there has been significant infilling by sediments
How may did the tombolo at Chesil beach form?
Thought to have formed during the Flandarian Transgression. Sediment carried into English channel by meltwater accumulated at Lyme bay, as sea levels rose they were pushed onshore by south-westerly prevailing winds, travelling 50km before attaching to mainland and Isle of Portland
How much shingle is found at Chesil beach?
estimated 100 million tonnes, ranging from1-3cm to 5-7 cm
It was previously thought that the tombolo at Chesil beach was formed by a spit? but why has this idea changed?
lack of recurves and complex grading of pebbles suggest it wasn’t formed by longshore drift alone
How may the gradient of fjords and rias change over time?
They become exposed to wave processes and sub-aerial processes in todays climatic conditions. This may lead to reduction in the steepness of valley sides
How may climate change impact fjords and rias?
water depth may increase due to a rise in sea level. Also, marine erosion more likely due to stormier conditions and larger waves
describe 2 ways in which a tombolo may be affected at a Shingle beach
- Shingle may travel further north east with current rates at around 17cm a year
- breach may be more likely due to rise in sea levels, with waves topping tombolo
what type of sediment addition may become likely in the future? give an example
addition of sediment during storm events and higher sea levels, e.g. in 2009, 1 meter-sized shelly clay eroded on a beach and washed up West Bexington in a winter storm, supposedly.
