Chapter 3 Flashcards
(22 cards)
Sea level rise
Increase in global temp
Higher rates of melting to ice stores, valley glaciers etc
Global increase in volume of water
Temp rises = h20 expand
1 degree rise in mean global temp= sea level rise of approximately 2m
Submergent landforms
Sea level rises
Ecstatic rise in sea level takes place faster than isostaic rebound after ice age
Flooding
Types of submerge the landforms
Rias
Fjords
Shingle beaches
Rias
Eg kings ridge
Submerged river valleys - winding reflects original route of river
Lowest part of the rivers course and the flood plains alongside the river may be completely drained
Higher land forming the tops of valley sides and then middle and upper port remains exposed
Exposed valley sides are gently sloping
Cross section of rias
Shallower water increasingly deep towards centre
Long section - Dias
Smooth profile and water of uniform depth
Fjords
Eg Milford sound fjord , NZ
Submerged glacial valleys
Steep, cliff like valley sides
Water is uniformly deep, reaching 1000m plus
U shaped cross section reflects original shape of glacial valley
Glacial rock basin with a shallower with a shallower end known as the threshold
Results from lower rates of erosion at seaward end of valley where ice thinned in warmer condition
Shingle beaches
When sea level falls as volume of land based ice grows and large areas of new land emerge from sea
Sediment accumulates on the surface, deposited by rivers, meltwater streams and low energy waves
As sea levels rose at the end of the last glacial period, wave action pushed these sediments onshore- beach at former cliff lines elsewhere may form bars and Tombolos
Modification of rias and fjords
May be modified by the wave processes acting on their sides at sea level
Valley sides - subariel processes May lead to steepness reduction in fjords
Sea levels- rise by 0.6m in 100 years, wave depth increase and increase in marine erosion
Shingle beaches modification
Longshore drift
Sea level rise increase
Storm events
Unconsolidated material - vulnerable
Eustatic sea level change
Eustatic changes - changes in the volume of water in the global ocean store
Changes influenced by variation in mean global temps - affecting BOTH amount of water in ocean store and its density
Also affected by isostatic changes( land level) ( sea level change) but NOT considered here
Factors that affect changes in global temp and water volume
Variations in the earths orbit around the sun , typically every 400,000 years
Variations in the amount of energy produced by sun, solar maximum every 11 years
Changes in composition of the atmosphere due to major volcanic eruptions which reduce incident solar radiation
Variations in tilt of the earths axis- every 41,00o
Glacial
A time where ice coverage on earths rise to significant levels
Inter glacial
Time where glaciers/ ice coverage has melted and sea levels are rising
Climate change and sea level
Decrease in global temp = more precipitation as snow
Snow turns into ice and water is slowed as solid rather than returned to sea
Reduction in volume of h2o in ocean store and fall in sea level
EMERGENT landforms- inland
Raised beach, marine terraces, and abandoned cliffs
Raised beaches are areas of formed shore platforms
Found inland from present shoreline- left high and dry
Behind beach - abandoned cliff with wave cut notches , caves , arches and stacks
Marine terraces are much larger scale landscape features than raised beaches which are quite small scale and localised at base of relic cliff
Terraces - form same as raised beaches - often don’t have cliffs above them
Modification of emergent landscapes
After their emergence these landforms are no longer affected by wave processes
Continue to be affected by mass movement and weathering
Post glacial period = warmed and wetter= vegetation for cover
Future - more earn confusions , increased Chemical weathering- cojld lead to increased sea level = wave processes , hot= chemical ( carbonation) and biological ( organisms on surface)
AFFECTed by waves agai
Geology at isle of purbeck
Green sands Purbeck and Portland limestone R London clay Kimmerage clay Chalk R Bagshot bed Wealden sands and sands Blown sands
Energy- Isle of purbeck
Wave processes bringing MOST of energy
Dominant wave direction is SW/S=long fetch = destructive waves
High transportation because of high erosion
Sediment trapped and deposited in bags between headlands eg lulworth and swan age
Wave height exceeds 3.5m at times
From south - concordant(P&P limestone
From east - disconcordant
Sediment sources- Isle of purbeck
Portland bill to selonely bill sediment cell
Net increase of sediment
10,000 - end of last ice age = English Channel flooded= sediment
Fluvial sources - river piddle
Nearshore stores - driven into coastline during storms
Cliff- erosion
Landforms( erosional) at Isle of purbeck
Headlands and bays eg st aldhems point headland and swan age bay
Stacks and stumps - chalk, eg old Harry’s rocks
Cliffs and shore platforms - Portland limestone eg golden cap
Arch - purbeck limestone eg durdle door
Depostiional landforms at Isle of purbeck
Beaches
- blown sands, green sands, Wealden sands and clays eg swanage beach
Spit
- blown sands eg stud land spit
Sand dunes
- blown sands eg studland dunes
Berms
- shingle beaches
