Role Of Sea Level Change

Question 1

What is isostatic change?

Answer 1

• The land rises or falls relative the sea
• localised change

Question 2

Process of isostatic sea level change?

Answer 2

• often a result of isostatic subsidence = ice thickness increases so the land is lowered
• tectonic activity (earthquakes + volcanic eruption) may cause land subsidence, therefore causing isostatic sea level chnage

Question 3

What is eustatic change?

Answer 3

• refers to global change in sea level

Question 4

Process of eustatic sea level change

Answer 4

• temperatures rise, ice melts through thermal expansion = sea level rises
• temperature decreases, glaciers + ice sheets advance = sea levels fall

Question 5

Sequence of sea level change

Answer 5

1. Temperature decreases, glaciers + ice sheets advance = sea levels fall eustatically
2. Ice thickness increases + land is lowered isostatically
3. Temperature rise, ice melts + sea levels rise eustaticslly
4. Continued melting releases pressure on the land + the land rises isostatically

Question 6

What are emerged coastlines?

Answer 6

• where the land has been raised in relation to the coastline
• landforms such as arches, stacks + stumps may be preserved

Question 7

Features of emerged coastlines

Answer 7

• raised beaches
• coastal plains
• relict cliffs
• raised mudflats

Question 8

What are submerged coastlines?

Answer 8

• occur when sea level rises or coastline sinks in relation to the sea

Question 9

Features of submerged platforms

Answer 9

• rias = flooded river valleys
• fjords = flooded glacial valleys
• Dalmatian coats = valleys parallel to the coast flooded creating a series of narrow, long islands

Question 10

How do Fjords form?

Answer 10

• glaciers erode u-shaped valleys by eroding away rock from the valley floor + side = creating deep, steep-walled valleys
• as glaciers melt, sea levels rise, the water enters the previously eroded valley flooding them
• fjords are typically deeper than the surrounding sea because the glaciers eroded the valleys far below sea level

Question 11

How do rias form?

Answer 11

• formed by submergence of coastal river valleys due to rising sea levels
• sea level rises due to eustatic or isostatic changes
• eustatic = changes in sea levek caused by melting glaciers or isostatic = changes in land relative to sea level when land subsides due to ice melting
• as sea levees rise low lying coastal areas including river valleys become flooded = forming a ria
• usually v-shaped cross section

Question 12

How do raised beaches form?

Answer 12

• sea level change eustatically or isostatically leads to either the fall of sea level or uplift of land relative
• causes the previously submerged beach to be raised above present waterline