Sea Level Change - Causes

Question 1

How have sea levels changed over the last 20,000 years?

Answer 1

Fastest and largest change in sea level

Question 2

Causes of sea level change - Tectonic

Answer 2

• a coastal region experiencing seismic activity (earthquakes) may experience land being shifted upwards or downwards as geological pressures are released and rocks adjust either side of fault lines
• as a result, there can be rapid change in relative sea-level, but over a relatively localised area

Question 3

What is a eustatic change?

Answer 3

• A global change in the sea level resulting from a change in the volume of water in the oceans.
• (e.g. thermal expansion/contraction and melting ice)

Question 4

What is thermal expansion/contraction?

Answer 4

• the biggest single factor responsible in the last 300 years
• as water becomes warmer it occupies a larger volume

Question 5

What is melting ice?

Answer 5

• the second largest factor
• increasing volume of the world’s oceans as water is redistributed from polar ice sheets and continental glaciers as they melt

Question 6

What is isostatic change?

Answer 6

• Local change in sea level resulting from the movement of the land relative to the sea
• the crust is ‘floating’ on the mantle beneath, and when weighted (by an ice sheet), it is depressed into the mantle - resulting in a rise in sea level.
• if the weight is lifted (ice sheet melts), the crust ‘rebounds’ and rises - creating a fall in sea level