COASTS PT.2 (climate + humans)

Question 1

what is a eustatic change?

Answer 1

A change in volume of water in global ocean stores

Question 2

what are eustatic changes influenced by?

Answer 2

Variation and mean global temperatures affecting amounts of water in ocean stores and its density

Question 3

what two things change sea levels?

Answer 3

-Land level
-Temperature

Question 4

what is isostatic?

Answer 4

When sea level changes is affected by land levels

Question 5

What four physical factors affect volume of ocean water

Answer 5

1. eccentricity.(400,000 years.)
2. Variation and amount of energy from sun (solar maximum every 11 years)
3. Changes in earths atmospheric composition due to major volcanic eruptions, which reduce solar radiation.
4. Variation in tilt of us axis (obliquity)(41,000y)

Question 6

why do sea levels fall?

Answer 6

-Decrease in global temps= more precipitation form of snow which turns to ice so water is stored on land
-Results in a reduction of water volume in ocean stores so sea levels fall

Question 7

what happens as temperature fall to water

Answer 7

water molecules contract leading to increased density and a reduced volume of water
-Estimated 1° C fall in global temps= sea levels fall 2 m

Question 8

when did sea levels rise(period)

Answer 8

-130,000 years ago during the tyrrhenian inter glacial global temperatures were 3° C higher than today’s and sea levels were 20 m above today’s

Question 9

when did sea levels fall? (period)

Answer 9

-during the riss glacial 108,000 years ago, temperatures were 7° below today and sea levels dropped by over 100 m which is 83 m below today

Question 10

what are emergent landforms?

Answer 10

They’re shaped by wave processes during times of high sea level and are left exposed as a seafood. As a result they are found well in land.

Question 11

what are three examples of emergent landforms

Answer 11

-Raised beaches
-Marine terraces
-Abandoned cliffs

Question 12

what are raised beaches?

Answer 12

Areas of former Shaw platforms that are left at a higher level than the present sea level. They are found in land far from the current coastline.

Question 13

How are raised beaches formed?

Answer 13

At the highest sea level waves pound against the cliff edge and create a normal beach below when the sea drops the original beach is left high and dry, and the new lower beach is formed

Question 14

Where are abandoned cliffs found?

Answer 14

Behind beaches on emergent coastlines

Question 15

what are abandoned cliffs often found with?

Answer 15

-wave cut notches
-caves
-arches
-stacks

Question 16

what are marine terraces?

Answer 16

Largest scale landscape features

Question 17

how are marine terraces formed?

Answer 17

The same as a raised beach, so marine erosion during periods of high sea level

Question 18

what can be found on the southern tip of Isle of Portland? (how long ago was it formed and how)

Answer 18

Raised beach, 15 m above the current sea level
-was formed 125,000 years ago during tyrrhenian interglacial period
-Portland limestone, eroded by hydraulic action through exploitation of the bedding planes weaknesses
-Erosion rates at this time=1m/year

Question 19

What happens to landforms after they emerge?

Answer 19

They are no longer affected by wave processes, and now affected by mass movement and weathering

Question 20

what is cryoturbation

Answer 20

Evidence of contortions and fragmented limestone as a result of freeze thawing of permafrost

Question 21

what happens to the emergent landforms if there is further warming

Answer 21

-Predicted, continued degradation with chemical weathering, and biological weathering on raised beach becomes more significant with the colonisation of surface by increasing numbers of marine of organisms, such as an limpets

Question 22

What would be the effect of rising sea levels to emerging landforms?

Answer 22

Would lead to these emergent landforms being found much closer to the coastline, where they are subject to more wave processes

Question 23

what is modification of emergent landforms PSD?

Answer 23

-on top of abandoned cliff on Isle of Portland is a 1-1.5m layer of frost shattered limestone debris deposited when it experienced periglacial conditions during the last glacial period

Question 24

what is a submergent landform?

Answer 24

Where coastline is submerged and landforms shaped by rises in sea levels

Question 25

what are two submergent landforms

Answer 25

-rias
-fjords

Question 26

what are rias?

Answer 26

Submerged River valleys formed a sea level rises

Question 27

what parts of rivers course remain exposed on rias

Answer 27

-valley sides
-middle
-upper part

Question 28

what’s the shape of a ria

Answer 28

exposed valley sides are gently sloping
-Plainview= winding, and reflecting the original route of the rivers and its valley

Question 29

what is a ria formed by?

Answer 29

fluvial erosion within the channel and sub aerial processes on Valley sides

Question 30

what are rias typically underlain by and what happened when sea levels rose

Answer 30

Alluvial deposits in channels that were eroded by rivers that flowed down low sea levels of pleistocene glacial periods
-When sea levels rose, further deposition would ever occurred, as rivers, had less surplus energy for erosion.

Question 31

What are fjords?

Answer 31

Submerged, glacial valleys that have steep cliff like valley sides

Question 32

what is the water depth of a fjord?

Answer 32

water is uniformly deep often reaching over 1000 m

Question 33

two examples of PSD for fjords

Answer 33

-sogne fjord - Norway = 200 km long
-Milford sound-New Zealand

Question 34

what reflects the original shape of the glacial valley on a fjord?

Answer 34

the U-shaped cross-section

Question 35

what features does a fjord have

Answer 35

-glacial rock basin with a shallow section at end, known as a threshold which results in lower rates of erosion at sea ward end of valley, where ice thinned in warmer conditions

Question 36

why are fjords straighter than rias?

Answer 36

They have straight planforms as glacier would have truncated any interlocking spurs present

Question 37

why did Marine erosion rates remain high in fjords

Answer 37

-due to depth of water that occupied fjords in flandrian transgression

Question 38

PSD- a fjord that has been infilling

Answer 38

-south coast of new zealand have been infilling with sediment

Question 39

Why do you sea levels rise?

Answer 39

an increase in global temperatures= Higher rates of melting ice stored on land, or in ice sheets, caps or valley glaciers
-So there’s a global increase in volume of water in the oceans, causing sea levels to rise
-Temperature rise, causes water, molecules to expand so increase volume of water in oceans

Question 40

what were the conditions during the würm period and what was this period called

Answer 40

-9° C lower than today
-Sea levels = 90 m lower than today
-flandrian transgression= sea level rise from 25,000 years ago during the würm glacial period

Question 41

how are shingle beaches formed?

Answer 41

-When sea level fall areas of new land emerge
-Sediment accumulates on this surface deposited by rivers, melt water streams and low energy waves
-As sea levels rose at end of last ice age wave action pushed sediment on shore
-some places sediment was beached at the base of cliffs elsewhere. They formed Tombolos or bars.

Question 42

PSD of shingle beaches

Answer 42

-Tombolo at Chesil Beach
-Thought to informed during flandrian transgression
-lyme Bay beach contains hundred million tons of shingle varying from 1-2 cm to 5-7 cm.

Question 43

what modification will happen to rias in the future?

Answer 43

-modified by wave processes, acting on sides at present day sea level
-Also affected by sub aerial processes
-Water depth will increase
-Increase in marine erosion due to more storm action

Question 44

how will fjords be modified in the future?

Answer 44

-Modified by wave processes, acting on sides at present day sea level
-Also affected by sub aerial processes, which will eventually lead to a reduction in steepness of the valley side
-Water depth will increase
-Increase in marine erosion due to more storm action

Question 45

how will shingle beaches be modified in the future? PSD

Answer 45

as they are made of loose material, they are vulnerable to modifications
-PSD- Chesil Beach Tombolo is affected by longshore drift and is likely to be affected in the future
-With sea levels, rising shingle may be moved further north east, with a current rate of 17 cm per year
-Breach of Tombolo is likely storm events
-In 2009, 1 m sizes of Shelly clay were eroded from in front of the beach and washed up onto the west bexington in a winter storm. sediment addition will become more common in the future with high sea levels and more storms 

Question 46

what is hard engineering?

Answer 46

Working against natural systems and processes

Question 47

what is soft engineering?

Answer 47

Working with natural systems and processes

Question 48

what are hard engineering management strategies?

Answer 48

CLIFF FOOT + BEACH STRATEGIES
-offshore breakwaters
-Embankments
-gabions
-revetments
-rip rap
-sea walls
CLIFF FACE STRATEGIES
-cliff drainage
-Cliff fixing
-Cliff regrading

Question 49

What is soft engineering beach management strategies?

Answer 49

-Beach nourishment
-Beach reprofiling
-Dune regeneration
-Vegetation planting
-Encouraging natural defences(reefs/mangroves)
-Offshore reefs

Question 50

how does a seawall work?

Answer 50

As a layer between vulnerable coastline and ocean
-It reflects energy back to sea
-Helps insulate communities from flooding. However, high waves can still breach the seawall.
-Several lower barriers may be used to help break up wave energy before the waves hit the wall
-The wall will eventually breakdown and require repair