Coastal Landscapes 1.3 Flashcards
What factors affect changes in global temperature and the volume of water in oceans?
Variations in the earths orbit around the sun - typically every 400,000 years
Variations in the amount of every produced by the sun - solar maximum every 11 or so years.
Changes in the composition of the atmosphere due to major volcanic eruptions
Variations in the tilt of the earths axis, occurring every 41,000 years
How does climate change cause sea levels to fall?
Decrease in global temperatures causes more precipitation being stored in the form of snow - This then turns to ice rather than returning to the sea as liquid - this reduces the volume of water in the ocean store - 1 degree fall causes 2m drop
what are emergent landforms?
Landforms shaped by wave processes during times of high sea level are left exposed when the sea level falls - they may be found well inland
Give 3 examples of emergent landforms
Raised Beaches - Former areas of shore platform now at a higher level than sea level.
Marine Terraces - larger scale of raised beach which tend to be small and localised - don’t always have cliffs above - formed through marine erosion during a previous period of higher sea level
Abandoned Cliffs - Where the sea level has dropped leaving these cliffs inland - common to find wave cut notch/ caves
What is the ‘modification of landforms’?
Where emergent landforms continue to be modified by weathering and mass movement
Portland - 1.5m of frost shattered limestone due to periglacial conditions - cliff also degraded by frost weathering processes - cryoturbation on the main face (contortions in limestone due to freeze thaw)
Post-glacial period - warmer and wetter conditions lead to the development of vegetation cover - further warming will led to degradation through chemical weathering - also more significant biological weathering
How does climate change cause sea levels to rise?
Increase in temperature causes a higher rate of melting of ice stored on the land in ice sheets/ice caps/valley glaciers - causes global increase in volume of water in the ocean store.
as temperatures rise water molecules expand leading to an increase volume of water - 1 degree of rise in mean global temp causes a 2m sea level rise
What is a ria?
A submerged river valley formed as the sea level begins to rise.
How is a ria formed?
As the sea level rise post a glacial period it will flood the floodplain and lower course of the river - upper/middle course and higher valley sides usually untouched - they have relatively shallow water becoming increasingly deeper nearer the centre
What is a fjord?
Fjords are submerged glacial valleys which steep almost cliff like valley sides with the water being uniformly deep often over 1000m.
How is a fjord formed?
During previous glaciated periods when the glaciers have then retreated and the rising sea levels have filled the valley they left behind.
Some were further deepened during the Flandrian Transgression when marine erosion rates remained high.
How are shingle beaches formed?
When sea levels fall due to the volume of land-based ice growing - areas of ‘new’ land emerge from the sea - sediment accumulates on the surface deposited by rivers- as sea levels rose at the end of the last glacial period wave action pushed these sediments onshore - they beach themselves at the base of cliff lines or form tombolos and bars.
Chesil Beach Tombolo - 100 million tonnes of shingle - sediment moved 50km before settling
How are Ria’s, Fjords and shingle beaches affected by modification?
Ria’s - Wave processes acting on valley sides - operation of sub-aerial processes on valley sides.
Fjords - Wave processes acting on valley sides - operation of sub-aerial processes on valley sides which may lead to reduction in steepness of fjord valley sides - sea levels predicted to rise 0.6m in 100 years causing fjords to deepen.
Shingle Beaches - continue to be effected by LongShore Drift as they are made of unconsolidated material - makes then vulnerable to modification - Chesil Beach shingle to be moved further northeast - recent storms have seen overtopping - more sediment action, higher sea levels and more storm events to be common in the future.
