Sea level change Flashcards
Name 3 factors effecting sea level change
- high & low tides
- atmospheric air pressure
- winds
Definition of isostatic change
local rise/ fall in land level
-occurs when crust is forced down into mantle changing relative sea level
Definition of eustatic change
rise/ fall in water level
-caused by change in vol of water
Name 3 reasons for contemporary sea level change
global warming- melting of- mountain glaciers, polar ice sheets- increasing amount of water in ocean
- thermal expansion- increases oceans temperature- causing water to expand
- tectonic activity- geothermal heat- water to expand
When do emergent coastlines form
- when water level has fallen- exposing land previously covered by sea
- when land has risen
What are emergent coastlines
coastlines that have formed where water level has fallen/ land has risen
-happens due to isotatic change
What are submergent coastlines
coastlines that have been flooded due to rise in sea levels
-happens due to eustatic sea level change
Name 2 emergent coastline landform and how it forms
-raised beaches- as land rises due to isostatic recovery- beaches are raised above present sea level
-Fossil cliff
a steep slope found at the back of a raised beach, above tide level
Name 3 submergent coastline landform and how it forms
-rias- form when valleys in dissected area are flooded
(example- kingsbridge devon)
- dalmatian coasts- rivers flow parallel to coasts (Dalmatian coast- Croatia)
- fjords- form when deep glacial troughs are flooded by rise in sea level (Norway)
When does a eustatic rise in sea level occur
- end of glacial period -> melting ice sheets return water to sea -> sea levels rise
- global temp increases -> vol of ocean water increases -> sea levels rise
When does a eustatic fall in sea level occur
-during glacial periods -> ice sheets form on land -> water evaporates from sea -> locked on land as ice -> fall in sea level
When does a isostatic rise in land level occur and what does this cause for sea level
- post glacial adjustment- where earths crust was formerly depressed under ice sheets, crust rises as ice sheets recede -> fall in sea level
- accretion-sink regions in sediment cell are experiencing deposition -> land built up -> fall in sea level
What is a ria
drowned river valley caused by sea level rise
What are barrier islands
offshore sediment bars
Name 2 reasons for longer-term sea level change
- eustatic change
- isostatic change
How does global warming affect sea level change
- > eustatic sea level rise
- > melting of mountain glaciers, polar ice sheets -> water in the ocean store increases
- > thermal expansion of existing ocean water as its temp rises
How does tectonic activity affect sea level change
- eustatic change -> emission of geothermal heat -> thermal expansion of ocean water -> rise in sea level
- isostatic change -> faulting uplifts sections of crust -> rise in land
What is post glacial adjustment
- process where earths crust was formerly depressed under ice sheers -> rises as ice sheets recede
- causes rise in local land level
What is accretion
sink regions in sediment cell are experiencing deposition -> land is built up -> decrease in seas level
When does a isostatic fall in land level occur and what does this do to sea levels
- subsidence -> deposition of sediment in large river deltas
- weight of sediment deposition overcomes threshold -> crustal sag
Give an example of an area where post-glacial adujustment is occuring, what is happening to this place
- Scotland is rebounding upwards
- due to rise in land level -> fall in sea lvel
Give an example of an area where accretion is occuring, what is happening there
contributed to chsnges hsown with river ZThames
-increased accumilation of sediment -> fall in land -> rise in sea levels
Give an example of an area in the UK that is sinking isostatically
(land is sinking)
Land’s End in Cornwall
Which part of Britain is experiencing isostatic fall in sea level
Northern Britain experiencing isostatic fall in sea level (land is rising)
Which part of Britain is experiencing isostatic rise in sea level
Southern Britain experiencing isostatic rise in sea level (land is sinking)
What are emergent coastlines prodcued by
post-glacial adjustment
Give an example of a raised beach and fossil cliff -> emergent landforms
Scotland, Fife
Give an example of a ria -> submergent landform
Kingsbridge, Devon
What are fjords
drowned glacial valleys
-always U-shaped
Give an example of a fjord -> submergent landform
Norway, Sognefjord
What are dalmatian coasts -> submergent landform
rivers flow parallel to coasts
How does global warming affect sea level change
- > eustatic sea level rise
- > melting of mountain glaciers, polar ice sheets -> water in the ocean store increases
- > thermal expansion of existing ocean water as its temp rises
How does tectonic activity affect sea level change
- eustatic change -> emission of geothermal heat -> thermal expansion of ocean water -> rise in sea level
- isostatic change -> faulting uplifts sections of crust -> rise in land
