Causes of Sea Level Change

Question 1

Name the 3 types of sea level change?

Answer 1

Eustatic changes.
Isostatic changes.
Tectonic activity.

Question 2

What are eustatic changes?

Answer 2

They are a result of global sea level changes.
During ice age = less water in ocean as precipitation falls as snow and joins ice on the land = sea levels fall.
When ice melts volume of water increases, sea levels rise - this can happen quickly.

Question 3

What other eustatic factor increases sea levels?

Answer 3

Global warming.
Partly due to thermal expansion of ocean as the water gets warmer.
Also due to melting of freshwater ice sheets. eg Greenland/

Question 4

What are isostatic changes?

Answer 4

They occur regionally/locally as a result of Earth’s crust.
Mainly the result of the weight of ice.
When large ice sheets cover the land it weighs down the land and makes it sink.
When ice melts the land will begin to rise as thr weight has removed.
This is called isostatic readjustment.

Question 5

Name a difference between eustatic changes and isostaic changes?

Answer 5

Isostatic changes occur much more slowly.

Question 6

What can isostatic changes also be a result of?

Answer 6

Tectonics.
eg sedimentation in a river delta - causes decline of land.
eg erosion from mountain chains - rise of land or volcanic action.

Question 7

What are tectonic activity changes?

Answer 7

They can result in eustatic sea level change over a long time period by decreasing and increasing size of ocean basins.
Meaning there is a larger or smaller area to contain the given volume of ocean.

Question 8

Give an tectonic activity example how sea levels have risen?

Answer 8

The emergence of the mid-atlantic ridge is of subterranean volcanoes and its likely to have causes a seal level rise of several hundred metres.

Question 9

Give a tectonic activity example how sea levels have fallen?

Answer 9

Spreading of ocean floors through plate divergence can result in eustatic falls in sea level.
Uplift of mountain ranges at destructive and collision plate boundaries.

Question 10

What is a relative rise and fall in sea level called?

Answer 10

Rise - positive movement of base level.

Fall - negative movement of base level.

Question 11

What is base level?

Answer 11

Lowest level to which a river can erode.