Coasts - Sea Level Change AGAIN Flashcards
What is isostatic change?
A change in sea level as a result of the changing level of the land.
What is eustatic change?
A change in sea level caused when the amount of water in the oceans changes.
Is isostatic change a local or global change?
Local
Is eustatic change a local or global change?
Global
When was the last glacial maximum?
18,000 years ago
What was the sea level like at the last glacial maximum compared today?
On average 110m lower than today
At the last glacial maximum, what joined the UK to mainland Europe and Scandinavia?
A large land bridge called Doggerland
How quickly are current sea levels rising?
3.2mm per year
What is the predicted rise in sea level by 2100?
4-6m
What is currently the main cause of rising sea levels?
Thermal expansion
Give 3 causes of isostatic change
- tectonic activity
- glaciation
- post-glacial readjustment
Give an example of tectonic activity causing isostatic change
Tohoku earthquake, Japan, 2011. Some sections of the coastline dropped by 0.84m.
How would glaciation cause isostatic subsidence?
The loading of a glacier or ice sheet’s weight onto the land causes the land surface to become pressed into the asthenosphere.
What is isostatic subsidence?
The falling of a land mass relative to the sea.
What is isostatic recovery?
The rising of a land mass relative to the sea.
How does post-glacial readjustment cause isostatic change?
The melting of glaciers and ice sheets on land allows it to rise back up as the asthenosphere rebounds.
Give an example of post-glacial readjustment causing isostatic change.
Currently causing sea levels to fall in Scotland. During the last ice age Scotland the part of the UK covered with the thickest ice which melted last. This is causing land in south east England to sink.
Give three causes of eustatic change.
- thermal expansion of water
- changes in ice sheet extent
- tectonic activity
How does thermal expansion cause eustatic change?
As water is heated it expands, increasing the volume of the water in the oceans. This causes sea level rise.
How do changes in ice sheet extent cause eustatic change?
Ice forming on land means water is removed from other stores such as the ocean, lowering sea levels. When ice on land melts it is then available to be stored in the oceans, which would increase sea level.
How does tectonic activity cause eustatic sea level rise?
New land formation under the ocean displaces water. This usually occurs at mid-ocean ridges.
What is total sea level change?
The balance between isostatic and eustatic change.
What is the total sea level change in Scotland?
Sea level is falling, as isostatic recovery is causing the land to rise at a higher rate than thermal expansion and melting ice sheets are causing the sea level to rise.
