Sea Level changes Flashcards
What is Eustatic Sea Level Change
Eustatic sea level change is caused by a change in the volume of water in the sea, or by a change in the shape of the ocean basins.
cause of Eustatic Sea level change
Changes in climate:
An increase in temperature causes melting of ice sheets, which increases sea level. It also causes water to expand, which increases sea level further.
A decrease in temperature causes more precipitation to fall as snow. This increases the volume of water stored in glaciers and so reduces the volume of the sea, which decreases sea level.
cause of Eustatic Sea level change
Tectonic movements of the Earth’s crust that alter the shape (and so the volume) of ocean basins
E.g. sea floor spreading increases the volume of the basin and so decreases sea level.
What is Isostatic Sea level change
Isostatic sea level change is caused by vertical movements of the land relative to the sea. Any downward movement of the land causes sea level to rise locally, while uplift of land causes sea level to fall.
Causes of isostatic sea level change
Uplift or depression of the earth’s crust due to accumulation or melting of ice sheets. Slow uplift of land can continue for thousands of years after the weight of a retreating glacier has gone. Accumulation of sediment, mostly at the mouths of major rivers, can also cause depression
Causes of isostatic sea level change
Subsidence of land due to shrinkage after abstraction of groundwater, e.g. drainage of marshland
Tectonic processes, e.g. as one plate is forced beneath another at a plate margin
Climate change has impact on coastal areas
1)Storms are likely to become more frequent and more intense due to changes in ocean circulation and wind patterns. This would cause damage to coastal ecosystems and settlements.
2)Major impacts on coastal areas:
More frequent and more severe coastal flooding (low-lying areas).
Changes in the coastline. Islands are created and the area of land is decreased.
Submergence of low-lying islands-low lying islands are at risk of disappearing.
3) Sea level rise and increased storminess will increase coastal erosion, putting ecosystems, homes and businesses at risk
Sea level fall results in coastlines of emergence
1)Raised beaches are formed when the fall in sea level leaves beaches above the high tide mark. Over time, beach sediment becomes vegetated and develops into soil.
2)Sea level fall also exposes wave-cut platforms, leaving them raised above their former level.
3)The cliffs above raised beaches are no longer eroded by the sea, and slowly get covered by vegetation. They’re called relict cliffs.
Sea level rise results in coastlines of submergence
Rias- are formed where river valleys are partially submerged. Rias have a gentle long- and cross-profile. They’re wide and deep at their mouth, becoming narrower and shallower the further inland they reach.
Sea level rise results in coastlines of submergence
Dalmatian coastline-In areas where valleys lie parallel to the coast, an increase in sea level can form a Dalmatian coastline. Valleys are flooded, leaving islands parallel to the coastline. It’s named after the Dalmatian coast in Croatia
Sea level rise results in coastlines of submergence
Fjords- are a lot like rias, but they’re drowned glacial valleys rather than drowned river valleys. They’re relatively straight and narrow, with very steep sides. They have a shallow mouth caused by a raised bit of ground formed by deposition of material by the glacier. They’re very deep further inland.
