Sea level change causes Flashcards
On what scale is isostatic change?
Sea level change on a local scale
On what scale is eustatic change?
Sea level change on a global scale (hollistic change)
What has happened to the global temperature overtime?
The global temperature has experienced periods of fluctuation between the glacial and interglacial periods due to the milankovitch cycles.
What happens to the global sea level during the glacial period?
The sea level goes down as more water is stored within ice.
What happens to the global sea level during the interglacial period?
The sea level increases as less water is stored in the ice.
What is the average rate of sea level rise?
Rising by 3.6mm per year
What is eustatic sea level change?
There is an alteration in the volume of water in the oceans or a change in the shape of an ocean basin (so there is a change in the volume of water the sea can hold).
What are the causes of eustatic sea level change?
- Changes in the air temperature
- The Albedo effect
- Thermal expansion
- Sea floor spreading and subduction
How do changes in the air temperature cause eustatic sea level rise?
During the glacial period, there is more ice so the sea level falls.
During the Interglacial period, there is less ice so the sea level rises.
How does the Albedo effect cause eustatic sea level change?
As the ocean warms, sea ice melts so the ocean is more exposed to infra red radiation as less is reflected by the ice sheets. This means that more sunlight is absorbed by the sea, causing it to warm and expand.
How does thermal expansion cause eustatic sea level change?
The process of water expanding when it gets warmer and so the volume of water increases leading to rising sea levels.
How does sea floor spreading and subduction cause eustatic sea level change?
-If tectonic plates move apart through sea floor spreading, the area of the area ocean increases, reducing the sea level.
-If tectonic plates move together and one subducts under the other, then the area of the ocean is reduced, increasing the sea level.
What is isostatic sea level change?
The increase or decrease in the height of the land: when the height of the land increases the sea level falls, when the high of the land decreases the sea level rises.
What are the causes of isostatic sea level change?
The weight of ice:
1. During peak glaciation, the weight of the ice depresses the land mass
2. During deglaciation, the area that once has glaciers rebounds (isostatic rebounding) and recovers slowly over time.
How does isostatic sea level change vary across the UK?
1.Land in the north and west of the UK is still rising as a result of isostatic. recovery.
2.Land in the south and east is sinking - this land faces increased flood risk.
