1: Coastal Sea Level Processes

Question 1

What are the 4 timescales that sea level change processes can operate at and what type of changes occur at each?

Answer 1

Millions of years = plate tectonics
Quaternary = eustasy
Holocene = isostasy
Current/future = steric/glacial melt

Question 2

What is isostasy and what is eustasy?

Answer 2

Eustasy = changes in the global sea volume in ocean basins that causes the underlying mantle response to change and thus shift the crust around and thereby areas that have sea above change in elevation
Isostasy = local response/adjustment of crust in response to local changes in ice volume causing density changes

Question 3

What is terrigenous and carbonate rock?

Answer 3

Terrigenous = sedimentary based rock eroded from the land
Carbonate = rock that typically forms from biological or chemical processes

Question 4

Outline the state/response of terrigenous coastline at low, transgressive and high sea levels

Answer 4

Low = terrestrial rivers incise in to the landscape due to greater GPE deriving from the lower sea level that it is trying to reach. A wedge at the marine/continental margin forms where the fluvial river deposits

Question 5

Outline the state/response of terrigenous coastline at a transgressive sea level

Answer 5

Transgressive = the higher sea level means that marine deposition occurs on the near continental landscape and so the previously created wedge is now starved of fluvial sediment and is now deposited further up on the land

Question 6

Outline the state/response of terrigenous coastline at a high sea level

Answer 6

High = once the higher sea level becomes stable the deposition upon the submerged landscape constantly grows so that now the fluvial system can extend further out towards sea and a new wedge can form further out than the very first wedge

Question 7

Outline the state/response of carbonate coastline at a low sea level

Answer 7

Because carbonate coastlines are usually steeper than terrigenous, the lower sea level means that only a narrow coral reef platform occurs at the base of a karstic cliff

Question 8

Outline the state/response of carbonate coastline at a transgressive sea level

Answer 8

As sea level rises the shallow marine environment upon which coral reef environments grow is now higher up on the karstic coastline and so a new reef grows on top of the narrow previous coral reef as well as on top of the karstic shelf which now lies just below the sea level mark

Question 9

Outline the state/response of carbonate coastline at a high sea level

Answer 9

Reef continues to grow on top of the reef that was growing previously during the transgressive phase. Essentially the reef just keeps growing and becoming more diverse

Question 10

Who was the first to identify potential glaciation cycles and how did he identify them?

Answer 10

Louis Agassiz investigated glacial moraine deposits in the Alps

Question 11

Who followed on Agassiz’s work first and what did they do?

Answer 11

Penck and Bruchner (1909) investigated the Alps as well and they identified 4 glaciation phases

Question 12

What did Zeuner (1945) do?

Answer 12

They investigated successive marine deposits in the Mediterranean to identify previous sea level standstills which were taken to signify previous interglacials

Question 13

What did Chappelle investigate?

Answer 13

A series of uplifted coral reef deposits in Northern PNG which contained evidence for previous interglacials and therefore glacials

Question 14

What are the current main form of palaeo evidence for glacial/interglacial investigations and why?

Answer 14

Marine deposits because they preserve a lot better than glacial deposits that are continually reworked through successive cycles.

Question 15

What is commonly contained within marine deposits and what can their composition tell us about the glacial/interglacial cycle?

Answer 15

Foraminifera - they are composed of oxygen isotopes which responds to ocean temperature which is taken as a proxy to represent glacial/interglacial cyclicity

Question 16

What are the main drivers of the glacial/interglacial cycle?

Answer 16

Milankovitch cycles

Question 17

What are the 3 different milankovitch cycles and their periodicity?

Answer 17

Eccentricity = 100ka
Obliquity = 41ka
Precession = 27ka

Question 18

What are jumps in the recorded depths of the global coral reefs an inferred signal for?

Answer 18

Meltwater pulses - where they jump in depth this shows that sea level likely jumped very quickly possibly due to a massive meltwater pulse

Question 19

When is coral reef depth shown to stop changing?

Answer 19

From 5000 years ago

Question 20

What is happening around the British Isles in regards to SLR and why?

Answer 20

Scotland is rising but surrounding areas are falling due to isostatic adjustment

Question 21

What evidence is there that sea level used to be higher 7ka?

Answer 21

Coral reefs above the sea/on the land have been dated to a significant age

Question 22

How has sea level change affected geographical distribution of landmasses?

Answer 22

Some areas become separated or joined in response to slr/fall

Question 23

Where is there a concentration of tide gauge networks?

Answer 23

Western Europe

Question 24

Give two examples of where Sea level change is clearly globally variable

Answer 24

Stockholm = sea level fall
Honolulu = sea level rise (due to massive volcanic weight causing crust around it to rise sharply)

Question 25

What is considered to be a better indication of sea level change and why?

Answer 25

Satellite altimetry (as opposed to tide gauge) because this records the entire ocean changes whereas tide gauges only record the changes at the coast