Coastal Landscapes and Change, Continued Flashcards
Sea level Change in General
long term sea level changes occur over thousand of years
long term sea level change is due to eustatic, isostatic factors and tectonics
tides, variations in air pressure and wind can create bulges in sea level
Eustatic Change
change in global sea level, due to a change of high volumes of water in oceans
how is water transferred (eustatic)
from land store back to oceans, increasing there volume of water in the oceans and raising global sea levels
how is a global fall in sea level achieved>
a decrease in the volume of water in the oceans
how much did sea level rise from 1870-2010
21cm - Humans are thought to be accelerating interglacial warming
Eustatic Rise in Sea Level
end of glacial period, melting ice sheets return water and sea level rise globally = global temperature rise = thermal expansion more water in ocean.
Eustatic Fall in Sea Level
ice sheets form on land, water evaporated from the sea is locked up on land as ice = sea level falls
What is isostatic change
change in local land level
local land level rise = sea level falls
post glacial adjustment
accretion - sink regions in sediment cell experiencing no deposition = land built up
tectonics
local land level falls = rise in sea level
subsidence
tectonics
post glacial adjustment
post glacial adjustment
weight of ice depresses the crust in areas below ice sheets = solid lithosphere forced down into asthenosphere
rigid nature of crust = sections of crust are depressed by ice adjacent areas are uplifted in seesaw affect
melting of ice effects - Post glacial adjustment
ice covered crust slowly rebound upwards whilst adjacent areas subside
UK - Ice Age
last ice age 12000
Uk covered with ice down to Birmingham
North Britain = isostatic fall in sea level, land lifted 1.5mm per annum
South Britain = isostatic rise in sea level, land lowered by 1mm
Tectonics and Eustatic Change
rising magma at constructive plates = reduce capacity of the ocean and produce eustatic sea level rise
uplift of crustal plate reduced Indian Ocean capacity - 0.1mm eustatic rise
Tectonics and Isostatic Change
Lava, Ash from volcanic activity produces isostatic fall, Hawaiian hot spot island chain
Sea floor spreading - carries volcanic island away from uplifted crust at mid ocean ridge, more dense crust subsides and sea rises, fIJI, Kiribati
Sedimentary rock folding at destructive plate produces an isostatic fall in sea level
Devonian Glacial Eustatic Change
sea levels lowered by 120mm
how are emergent coastlines produced
post glacial adjustment, parts of littoral zone where fall in sea level exposed land once part of sea bed
what is a raised beach
relict beach above high tide
flat surface covered by sand
usually vegetated by plant succession
what is a Fossil Cliff
steep slope found at back of raised beach exhibiting evidence of formation through marine erosion, now above sea level
may contain wave cut notches, caves, arches
Isle of Arran
raised beach 5m above sea level
Three levels of raised beach produced at different stages of post glacial adjustment
what is a submerging coastline
sections of littoral zone where sea level rise inundated areas that were previously part of terrestrial land
where are submergent coastlines found
southern England and east coast of America
what is a ria
drowned river valley - section of the river valley flooded by the ocean making it wider
where are rias common
periglacial areas that were adjacent to land covered ice during the devansian