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Sea level change
Why is sea level change important?
High population living in coastal areas.
Profoundly alters coastal system- everything changes- position of coast,
energy budgets, sediment budgets and coastal landforms.
Types of seas level change
Absolute change in the volume of water.
Oceans hold 97% of water and ice holds 2%. Changes in this balance caused
by changes in earth's temperature. This can raise or lower volume of oceans.
Temperature rise when glaciers and ice sheets melt increasing volume of
Thermal expansion- sea water expands, for every 1 degree C rise, sea levels
rise by 0.8m.
Temperatures fall and glaciers and ice sheets advance so sea levels fall.
During 20th century, sea levels rose by 15cm as climate continues to warm;
sea levels are predicted to rise a further 50cm by 2100.
Relative rise or fall of land. Movements can be tectonic or Isostatic. E.g.
Scotland had risen 40-50m in 12000 years and south England has sunk. Sea
levels fall in Scotland and rise in south England (Isostatic rebound)
Sea level change due to earth's crust rising and falling relative to sea level.
Caused by tectonic processes and depression of earth's crust into the
mantle due to weight of the ice sheet. When ice melts the weight is released
and the crust rebounds.
Scotland is now rising so the sea level is falling where as in the south east
of England it is falling and the sea level rising.
Outbuilding of the coast called progradation. Caused by sediment rich
rivers depositing large amounts of sediment into coastal rivers.
Landforms created by sea level change
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Drowned river valleys. Fluvial erosion creates deep river valleys, flooded
by rising sea levels. Flooding of main river valley and tributaries e.g. river
After ice sheets melted, wide valleys flooded forming wide, tidal, sediment
rich river mouths such as the Thames estuary.
In hilly areas, such as in Cornwall, rias formed. Lower sections of the river
valley flooded as sea level rose and picked out a pattern of former
tributaries forming a tidal inlet.
Rias become deeper as they enter the sea.…read more
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Response project-produce maps of existing information which can be used
to identify potential hazards, risks and inform planning.
HOLSMEER project- set up to investigate marine change in shallow coastal
areas. Data used o provide time markers of sea level change.…read more