Coastal Geography, Sea Level Change

Question 1

What are the three main causes of sea level rise?

Answer 1

Short term causes (tides, winds, floods), changes in water temperature (thermal expansion), and elevation in Equator due to increased temperature

Question 2

What are the three main types of long term change in sea level?

Answer 2

Changes in ocean basin volume, ocean water volume, and ocean distribution

Question 3

Ocean basin volume

Answer 3

Changes occur due to plate tectonics and isostatic adjustment

Question 4

Ocean water volume

Answer 4

Location of seafloor. Changes occur due to climate change and thermal expansion

Question 5

Ocean distribution

Answer 5

Changes occur due to effects of gravity/Earth’s rotation

Question 6

What is the most significant component of the hydrological cycle?

Answer 6

There is a finite anmount of water in the system, 97% of which is stored in the ocean

Question 7

Eustasy

Answer 7

The rise and fall of sea level due to changes in ocean volume

Question 7

Glacio-eustasy

Answer 7

The global change in absolute sea level caused by the melting or expansion of ice sheets

Question 8

Isostasy

Answer 8

The rise or fall in land due to changes in elevation of the Earth’s crust. This changes relative sea level

Question 8

Glacio-isostasy

Answer 8

The regional/local rise or fall of land caused by the melting or expansion of ice sheets

Question 9

What are the four primary long term controls on sea level?

Answer 9

Eustasy, glacio-eustasy, isotasy, and glacio-isostasy

Question 10

What were ice sheets like 20,000 years ago during the Last Glacial Maximum?

Answer 10

There were two major ice sheets (2Km thick) in the Northern Hemipshere which covered parts of North America and Russia

Question 10

What were the names of these two ice sheets?

Answer 10

North America: Laurentide ice sheet

Russia: Fennoscandian ice sheet

Question 11

What are the three relevant epochs of the geological timescale and what period do they belong to?

Answer 11

The Pleistocene, Holocene, and Anthropocene which all belong to the Quaternary period

Question 11

What is the general pattern of glacio-eustatic sea level rise?

Answer 11

Absolute sea level has always fluctauted but it was 120,000 years ago when present day sea levels can be observed

Question 11

What are two types of evidence for changing sea levels?

Answer 11

Past coastal stacks (both above and below sea) and unconvential forest locations

Question 12

Sea level stillstand in New Zealand and Australia

Answer 12

In New Zealand and Australia, sea level reached its current position 6000 years ago, rising 1.3m every century since the last glacial period. This has given New Zealand’s coasts 6000 years to change and develop

Question 13

How is the relationship between the Earth’s solid crust and fluid mantle similar to that of an iceberg in water?

Answer 13

Like an iceberg in the ocean, the Earth’s crust is displacing the mantle according to its bulk and density. Like an iceberg, removing weight from the surface will cause the submerged part to rise in order to maintain a floating balance. This is also similar to the 2Km thick ice sheets that were present in the Northern Hemipshere

Question 14

Why does sea level history vary between coasts?

Answer 14

Sea level history is not globally uniform due to regional differences in the presence of ice sheets. The Northern Hemipshere had two ice sheets 2Km thick whilst the Southern Hemisphere was not compltely glaciated

Question 15

Isostatic rebound

Answer 15

The slow rising of landmass after ice melts.

Question 16

How does isostatic background interact with different parts of a landmass?

Answer 16

Rebound is greatest in the centre of the landmass and decreases towards the coastline. This discrepancy in rebound essentially causes the coast to sink, subsequently causing sea level to rise.

Question 17

What are the two ways that the coast can respond to changes in sea level?

Answer 17

Transgression and regression

Question 18

Transgression

Answer 18

As sea level rises, the coastline retreats landward, taking sediment with it. Remnants of coastal features are left behind as relicts

Question 19

Regression

Answer 19

As sea level falls, the coastline is allowed to advance. This can also occur during periods of stable sea leve due to an abundance of sediment washing up onto the shore

Question 20

Is sea level rising?

Answer 20

Yes, and it has been doing so for the past century. However, there is much less certainty about the future