Causes of Eustatic and Isostatic Sea Level Change

Question 1

Name 3 ways that cause a eustatic sea level change?

Answer 1

Climate cooling.
Climate warming.
Steric effect.

Question 2

Climate cools.

Answer 2

More water locked up as ice, less in oceans.

Sea level drops.

Question 3

Climate warms.

Answer 3

Ice melts and volume of ocean water increases.

Sea level rise.

Question 4

Thermal expansion

Answer 4

Climate warms causing rise in ocean temperature.

Warming lowers density of water, upper parts of ocean heat up, they expand and increase total volume of oceans.

Question 5

Name 4 causes of an isostatic sea level change.

Answer 5

Tectonic activity.
Glacial rebound.
River and wetland modification.
Extraction of resources.

Question 6

Tectonic activity.

Answer 6

Uplift occurs in regions where oceanic crust is being forced beneath continental crust at collision margins.
Local tilting has led to submergence of several ancient parts of mediterranean sea.

Question 7

Glacial rebound/ isostatic readjustment.

Answer 7

Gradual rise of a specific area of land after an ice sheet that once weighed it down has melted.

Question 8

Example of Glacial rebound/ isostatic readjustment.

Answer 8

Scotland and Scandinavia rising by 4-20mm a year.

Question 9

River and wetland modification.

Answer 9

Heavy sediment loading in deltas can cause compaction and subsidence, lowering land surface and increase in sea level.
eg Mississippi Delta.

Question 10

Extraction of resources.

Answer 10

Removing ground water, fossil fuels, minerals and other resources from low-lying coastal areas - lead to subsidence.

Question 11

Eustatic rise in sea level

Answer 11

During end of ice age when climate gets water it causes terrestrial ice to melt and flow into oceans.
This increase the volume of water in ocean basin and ultimately leads to eustatic rise in sea level.

Question 12

Eustatic fall in sea level

Answer 12

During an ice age climate is a lot colder meaning less water stored in ocean as precipitation and snow joins ice on land and freezes.
Therefore hydrological cycle is suspended and there is a eustatic fall in sea level.

Question 13

Eustatic rise in sea level due to global warming

Answer 13

Global warming causes warmer climates and warmer oceans.
This warming causes oceans to expand exerting more volume in ocean basin and in cause eustatic rise in sea level - thermal expansion.
Also global warming melts freshwater ice sheets like Greenland and decreases their distance from ocean.

Question 14

When do isostatic changes occur?

Answer 14

During ice age glaciers compressed land causing it to sink - isostatic fall relative to see
When the ice melts the land begins to rise as weight is removed - isostatic readjustment - isostatic rise relative to sea

Question 15

What place is experience both isostatic fall and eustatic rise ?

Answer 15

London.
Eustatic rise due to warmer temps/ thermal expansion.
But also due to land subsiding.

Question 16

What change occurs more slowly V

Answer 16

Isostatic change occurs more slowly

Question 17

Isostatic changes can also be as a result of what ?

Answer 17

Tectonics

Question 18

How does tectonic activity result in eustatic sea level change ?

Answer 18

Decreasing and increasing size of ocean basin.
Meaning larger or smaller area to contain given volume of ocean

(Larger time scale)

Question 19

How can tectonic activity lead to eustatic fall ?

Answer 19

Spreading of ocean floors through plate divergence.

Uplifting of mountain ranges and costal land at destructive and collision plate boundaries.

Question 20

How can tectonic activity lead to eustatic rise in sea level ?

Answer 20

Emergence of mid Atlantic ridge is of subterranean volcanoes caused sea level rise of sevens hundred metres

Question 21

Negative movement of base level

Answer 21

Relative fall in sea level

Question 22

Positive movement of base level

Answer 22

Rise in sea level