Isostatic And Eustatic Change Flashcards
When does Eustatic change occur?
When there is a change in the volume of water in the ocean basins
When does Isostatic change occur?
When the height of the land changes relative to the water level - happens mor slowly
Why does Eustatic change occur?
Due to changes in the amount of ice as a result of thermal expansion and tectonics, this change will be global (eg. Last ice age 10,000 years ago global sea level rose rapidly due ro melting ice creating waterways like the English Channel)
What is thermal expansion?
Occurs was water warms, warmer fluids expand to take up a greater volume, magma rising ro the surface lifts the crust and reduces the capacity of the oceans causing sea level to rise
Why does Isostatic change occur?
When the glacial period ends and the ice melts, the land will renounce ro a higher level, lowering sea level in a process known as Isostatic recovery/rebound (post glacial adjustment, during a period of glaciation extremely heavy ice sheets weigh land down), localised change
What is accretion?
Within the sediment cell there are areas of net deposition causing land to build up
What is subsidence?
Causes by lowering of the water table or increase deposition weighing down the sediment
Explain tectonics:
The folding of the sedimentary rock, lava and ash from volcanoes increases the height of land relative to the sea level
Explain Isostatic change in the UK:
The UK is still experiencing Isostatic change from the end of the last ice age, land in north Scotland is still rebounding an rising by around 1.5 mm a year, lands end in Cornwall therefore is sinking by 1.1 mm each yeae
What are emergent coastline features?
Landforms that exist because of a reduction in sea levels, happens during Isostatic recovery, when land rebounds through Isostatic recovery
Explain raises beaches:
Beaches which are above high tide level, they are flat and covered by sand/pebbles, experiences succession
Explain fossil cliffs:
Steep slopes at the back of a raised beach, wave cut notches, caves and arches may be present
Explain submerging coastline features:
Landforms that exist because of a rise in sea level, this happens when coastlines flood, as a result of isostatic change
Explain a Ría/drowned river valley:
when coastal areas are flooded the lower course of the river valleys can be flooded creating them, has a V-shaped cross section, an estuarine coastline, are most common landform
Explain glacial valleys:
Flooded as a result of Eustatic change, creating a fjord, which are deeper and more inland as they here originally a flat bottomed U-shaped valley which is carved out by a powerful glacier, they have a relatively straight profile, maybe deeper than the adjacent sea
What are Dalmatian coasts?
Where landscapes of valleys and ridges are parallel to the coastline the low parts of the valleys will be flooded when sea levels rise, the exposed tops of the ridges become small offshore islands parallel to the coast, eg. Dalmatian coast in Croatia
