Sea level change Flashcards
What is eustatic change?
When the sea level rises or falls
What is isostatic change?
When land rises or falls, relative to the sea.
Eustatic fall in sea level
During glacial periods, when ice sheets form on land in high latitudes, water evaporated from the sea is locked up on land as ice, leading to global fall in sea level.
Eustatic rise in sea level
At the end of a glacial period, melting ice sheets return water to the sea and sea level rises globally. Global temperature increases cause the volume of ocean water to increase (thermal expansion) leading to sea level rise.
Isostatic fall in sea level
During the build up of land-based ice sheets, the colossal weight of ice causes the Earth’s crust to sag. When the ice sheets melt, the land surface slowly rebounds upward over thousands of years.
Isostatic rise in sea level
Land can ‘sink’ at the coast because of the deposition of sediment, espiecially in large river deltas where the weight of sediment deposition leads to very slow ‘crustal sag’ and delta subsidence.
What is post-glacial adjustment?
Refers to the uplift experienced by land following the removal of the weight of ice sheets.
Scotland is still affected.
In what way is Great Britain pivoting?
South sinking and North rising
What are rias?
Rias are drowned river valleys in unglaciated areas, caused by sea level rise flooding up the river valley, making it much wider than would be expected based on the river flowing into it.
What are barrier islands?
Offshore sediment bars, usually sand-dune covered but unlike spits, they are not attached to the coast. They are found between 500m and 30km offshore and can be tens of kilometers long
How do fjords differ from rias?
Drowned valley is u shaped glacial valley
Fjord is often deeper than the adjacent sea, some over 1000m deep.
At the seaward end of the fjord there is a submerged lip, representing the former extent of the former glacier that filled the valley.
What change in sea level will occur in 2100
Some scientists say that one meter.
