2B.7

Question 1

What plate boundary is NZ onc

Answer 1

convergent

Question 2

Describe tongue point, NZ

Answer 2

New Zealand
In the Cook Strait
Many steep cliffs with complex seabed

Question 3

Describe kaikoura, NZ

Answer 3

Experience 7.8 mag EQ in Nov 2016
4 different faults broke at once
Sea-bed is now 2m higher

Question 4

Define isostatic

Answer 4

A local change in sea level due to a change in local coastline or land height.

Question 5

What is the effect of isostatic change

Answer 5

• Heavy ice push land downwards
• North Britain was glaciated and pushed down, Britain’s south was ice free and tilted upwards slightly
• Melting ice means that glaciated land rebounds back whilst land that was tilted upwards starts to sink bank - post glacial adjustment

Question 6

What does isostatic change produce

Answer 6

Characterised by raised beaches / relict fossil cliffs
Now away from marine processes, and terrestrial processes operate instead.

Question 7

What is the tectonic influence on the seabed

Answer 7

Plate convergence / subduction causes sudden thrust / upward or downward movements of the sea-bed

Question 8

What are fossil cliffs

Answer 8

Near vertical cliffs initially formed by marine processes , but inland
Sometimes find old sea caves / wave cut platforms
- a steep slope found at the back of a raised beach exhibiting evidence of formation through marine erosion but now above high tide level.
- they may contain wave-cut notches, caves and arches providing evidence of formation by marine erosion
- episodic nature of isostatic recovery allows marine processes to erode cliffs and deposit beaches when sea levels are stable. Relatively rapid drop in sea level then leaves relict coastline abandoned above high tide and some distance inland

Question 9

What are raised beaches

Answer 9

Found above high-tide
Reflects a series of stages of uplift (as they consist of several different layers)
Smaller particles are removed by waves, leaving rounded pebbles / boulders

Question 10

State four characteristics of eustatic sea level fall

Answer 10

• Happens during glacial periods
• Ice sheets are formed on high-latitude land
• Evaporated water is locked up as ice
• Less water in the sea

Question 11

Why does eustatic sea level rise occur

Answer 11

• Interglacial periods - ice sheets on land melt
• Melted water returns to the sea, so sea-level rises
• Global temperatures also cause thermal expansion - water particles move faster and take up more space, increasing the volume of ocean water (i.e. global sea-level rise).

Question 12

Why does Isostatic sea level fall occur

Answer 12

• Ice sheets melt, and land surface slowly rebounds upwards – lifting the land surface out of the sea – sea level appears to fall.

Question 13

Why does isostatic sea level rise occur during glacials

Answer 13

During glacials: Land is compressed by the weight of glaciers, causing sea-level to appear to rise.

Question 14

How might isostatic sea level rise occur during interglacial periods

Answer 14

During interglacials: ice melts leads to sediment being deposited in large river deltas, leading to increased weight / ‘crustal sag’, and delta subsidence – sea-level appears to rise

Question 15

Describe missisipi river

Answer 15

Louisiana
- Mississippi River flows into the Gulf of Mexico
- Alluvial, depositional coast – marshes, swamps and barrier islands

Question 16

What is management of missisipi river like

Answer 16

Huge levees & engineering projects protect New Orleans to the North - upstream river management can deprive the delta of sediment - so becomes lighter and rises?…

Question 17

Describe post glacial rebound in usa

Answer 17

• northern part of the USA / Canada is rebounding upwards (relative sea-level fall),
• southern of the USA is tilting downwards (relative sea-level rise

Question 18

Why is historical land loss evident in south usa

Answer 18

eustatic SLR and isostatic tilt downwards in southern usa OR global SLR is cuased by thermal expansion

Question 19

What is the diff between eustatic and isosatic SLR in terms of region

Answer 19

Eustatic - global
Isostatic - localized

Question 20

What is missisipi river vulnerable to

Answer 20

Storm surges
Global sea level rise
Isostatic tectonic uplift

Question 21

What risk do storm surges post to missisipi river?

Answer 21

• Low-pressure storm surges, particularly from hurricanes can raise local-sea-level over the levees
• The impact of long-term sea-level change requires management: levees are built on the edge of the river. The city is built ‘below sea-level ref to slide 13 1.7 relatively sinking

Question 22

Define accretion

Answer 22

Accretion is the accumulation of sand or land mass over time along coastal regions. - idea of subsidence or ‘crustal sag’

Question 23

What does longer term changes result

Answer 23

complex interplay of factors:
- eustatic (ice formation/melting,
thermal changes)
- isostatic (post glacial adjustment,
subsidence, accretion and tectonics).

Question 24

How might a rise in local land level cause a fall in local sea level (isostatic)

Answer 24

• post-glacial adjustment
• accretion
  sink regions in the sediment cell are experiencing net deposition, land is built up, leading to a fall in sea level (in delta regions accretion -> subsidence -> accretion and so on)
• tectonics

Question 25

REF TO 2B.7A a level edexcel revisio weebly

Question 26

Describe eustatic fall in sea level

Answer 26

During glacial periods, when ice sheets form on land in high latitudes, water evaporated from the sea is locked up on land as ice, leading to global fall in sea level

Question 27

Describe eustatic rise in sea level

Answer 27

At the end of a glacial period, melting ice sheets return water to the sea and sea level rises globally. Global temperature increases and causes the volume of ocean water to increase (thermal expansion) leading to sea level rise.

Question 28

How does a fall in local land level produce a rise in local sea level (isostatic)

Answer 28

subsidence
- subsidence of land produces a rise in sea level
the deposition of sediment, especially fluvial deposits in large river deltas, the weight of sediment deposition overcomes the threshold and leads to very slow ‘crustal sag’ and delta subsidence, e.g. Nile, Mississippi, Amazon
- can also be caused by the lowering of the water table (from increased evaporation from climate change or human abstraction) can lead to settling of overlying sediment and land subsidence as pore water pressure is removed
-or by heavy buildings