Isostatic, eustatic, emergent and submergent

Question 1

What is eustatic sea level change?

Answer 1

This is when the sea itself rises and falls. The effects of this are always global and occur relatively quickly.

Question 2

How does climate change cause eustatic sea level change?

Answer 2

Climate change: Increased temp. causes melting of ice sheets which increases sea level. Also causes water to expand.
Decrease in temp. causes more precipitation to fall as snow, increasing volume of water stored in glaciers and reducing volume of sea

Question 3

How do tectonic movements cause eustatic sea level change?

Answer 3

These can alter the shape of ocean basins.

E.g. sea floor spreading increases the volume of the basin and so decreases sea level.

Question 4

What is isostatic sea level change?

Answer 4

When the land rises or falls relative to the sea. Downward movement of land causes sea to rise locally while uplift causes sea to fall.
The effects are always local and can take a longer time.

Question 5

How do ice sheets cause isostatic sea level change?

Answer 5

Uplift or depression of the earths crust due to melting or accumulation of ice sheets.
Slow uplift of land can continue for 1000s of yrs after weight of retreating glacier is gone.

Question 6

What, other than ice sheets, can cause depression of earths crust?

Answer 6

Accumulation of sediment mainly at the mouths of rivers.

Question 7

How does abstraction of ground water cause isostatic sea level change?

Answer 7

Subsidence (gradual caving in or sinking of land) of land due to shrinkage after ground water abstraction.
E.g. drainage of marshland

Question 8

How do tectonic processes cause isostatic sea level change?

Answer 8

Tectonic processes like one plate being forced under another at a plate margin.

Question 9

What isostatic sea level change is there in the UK?

Answer 9

During the ice age the north was covered in ice which then melted and the land is still going through isostatic recovery and rising as there is less pressure on the land from ice sheets.
The south east is sinking in relation to the north west.

Question 10

What is thermal expansion and how has effected earth is the past and today?

Answer 10

When water heats up it expands. Around 1/2 of the past century’s sea level rise is due to warmer water occupying more space.

The Greenland and Antarctic ice sheets are the largest bodies of ice in the world and have been losing large amounts of ice at an increasing rate since 1992.

Question 11

How much ice have the Greenland and Antarctica ice sheets lost?

Answer 11

Greenland has lost 3,600Gt from 1992 to 2015

Antarctica has lost 1,500Gt since 1992 contributing 5mm to sea level rise.

Question 12

What is an emergent coastline?

Answer 12

A stretch of coast that has been exposed by the sea by a relative fall in sea levels by either isostatic or eustatic change.
Land previously covered by the sea exposed.

Question 13

What landforms are associated w/ an emergent coastline?

Answer 13

• Raised beach
• Relic cliff
• Marine platform or terrace

Question 14

What is a submergent coastline?

Answer 14

A stretch of coastline that has been inundated by the sea by a relative rise in sea levels form isostatic or eustatic change.
It is a rise in sea level that floods the coast.

Question 15

What landforms are associated w/ a submergent coastline?

Answer 15

• Dalmatian coast
• Fjord
• Ria

Question 16

What is a fjord?

Answer 16

A submergent coastline.
Formed when a glacial valley floods. Steep sides and generally straight and narrow. The have a U shaped cross section. They have a shallow mouth due to a raised bit of ground formed deposition of material from the glacier. They are very deep further inland.
Sognefjorden in Norway is over 1000m deep in places.