Sea Level Change

Question 1

Sedimentary evidence for sea level change

Answer 1

• Sediment cores from the inter-tidal zone can be used to study sea-level change
• Change from saltmarsh clay to freshwater peat = negative sea-level tendency
• Change from freshwater peat to marine clay = positive sea-level tendency

Question 2

Geomorphological evidence for sea level change

Answer 2

Raised beaches
Submerged forests
Submerged peat beds
Raised wave cut platform

Question 3

Evidence for sea-level rise in the Mediterranean Sea (20 - 0 k yrs BP)

Answer 3

Med received large volumes of meltwater at

the end of the ice age

Question 4

Types of sea-level change in a glacial/interglacial cycle

Answer 4

• Eustacy = global change in ocean volume
• Isostacy = tectonic change in the level of
land relative to sea

Question 5

Eustatic sea-level change

• Glacio-eustacy

Answer 5

Sea-level change controlled by global build-up and

breakdown of ice sheets

Question 6

Other Eustatic controls

Answer 6

(1) Thermal expansion / contraction of sea water
(2) New water accretion from volcanoes
(3) Tectono-eustacy = global sea-level change caused by continental-scale tectonic activity
(4) Sedimento-eustacy = gradual in-filling of ocean basins with sediment

Question 7

Geoidal effect

Answer 7

• The sea is not distributed evenly
• An area around New Guinea is 180m higher than a trough just south of India!
• Sea-level - affected by Earth’s rotation & density (this varies)
• Changes in ice sheet size = major changes in gravity

Question 8

Glacio-isostatic rebound in Great Britain

Answer 8

Rebound over Scotland was relatively small
Ice sheet thinner than Scandinavian one
Centre of uplift corresponds to centre of the ice sheet

Question 9

Loading of the crust can also occur because

of:-

Answer 9

• Sediment accumulation (e.g. deltas)
• Flooding of continental shelf (Hydro-isostacy)
– Continental shelf is thin and flexible crust
– Accounts for several metres of altitudinal change

Question 10

There are four main controls on sea-level

Answer 10

– Eustatic processes that change global ocean volume
– Gravitational changes (e.g. caused by massive ice sheets)
– Tectonic changes that affect ocean basin size
– Isostatic displacement / rebound caused by crustal loading /unloading