Coasts- Sea Level Changes

Question 1

What is eustatic change?

Answer 1

A global change in sea level resulting from a fall or rise in the level of the sea itself

Question 2

What is isostatic change?

Answer 2

Local changes in sea level resulting from the land rising and falling relative to the sea

Question 3

Causes of eustatic change

Answer 3

• thermal expansion (where the volume of water increases at it gets warmer)
• land ice melt (melting of glaciers and ice sheets)

Question 4

Sea level changes during glacial periods

Answer 4

• global temp. cools down allowing ice to accumulate on land and form glaciers/ice sheets
• this reduces the water available to fill oceans so there is a eustatic fall in sea level due to glaciation
• the change is partly moderated by the ice forcing land mass down via isostatic change
• when climate warms ice melts and global sea levels rise quickly through eustatic change
• once ice is removed, isostatic rebound can occur (very slow takes thousands of years)
• prolonged rebound allows emergent features (eg. raised beaches) to now sit below sea level
• rising sea levels flood some coastlines to create submerging features (eg. fjords and rias)

Question 5

Formation of rias

Answer 5

• sheltered winding inlets with irregular shorelines
• form when valleys in a dissected upland area are flooded
• common in south west England

Question 6

Formation of fjords

Answer 6

• formed when a glacier retreats after carving its typical U-shaped valley and the sea fills the resulting valley floor
• forms a narrow steep sided inlet connected to the sea
• the terminal moraine pushed down the valley by the glacier is left underwater at the fjords entrance
• causes water at the neck of the fjord to be shallower than the main body of the fjord behind it

Question 7

Formation of relict/fossil cliffs

Answer 7

• old cliffs displaying features such as caves, arches and stacks which are now above sea level
• emergent coastal landforms
• sometimes found behind raised beaches

Question 8

Formation of raised beaches

Answer 8

• as the land rose as a result of isostatic recovery firmer wave cut platforms and their beaches were raised above the present sea level
• common on west coast of Scotland

Question 9

Formation of marine platforms/terraces

Answer 9

-a wave cut platform that now exists as an extensive flat area in front of a relict cliff above active wave action

Question 10

Dalmation coasts formation

Answer 10

• distinctive submergent coastlines that form in a landscape of ridges and valleys running parallel to the coast
• when the sea level rises, the valley floods but the top of the ridges remain exposed-form a series of offshore islands running parallel to the coast
• dalmation coats are often known as Pacific coasts

Question 11

What must happen in order for submergence landforms to form?

Answer 11

The sea level must rise or the land level must fall (this is unlikely)

Question 12

What must happen for emergence landforms to form.

Answer 12

The sea level must fall or the land level rise (more likely)

Question 13

What is subsistence of the coastline?

Answer 13

• coastal areas sinking
• often due to excess groundwater extraction
• has the effect of making the sea level higher

Question 14

How much is the sea level expected to rise in the next 70-80 years?

Answer 14

75cm