Beth- Physical Geography > Coasts- Sea Level Changes > Flashcards

Coasts- Sea Level Changes Flashcards

(56 cards)

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1
Q

What is a Eustatic sea level change?

A

One cause by the change in the volume of water in the sea or by the change in the shape of ocean basins

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2
Q

Are the effects of eustatic change always global or local?

A

Global

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3
Q

What are the 2 main causes for eustatic change?

A

Changes in climate
Tectonic movement

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4
Q

How does a change in climate affect sea level rise R?

A

-Increasing temps causes melting of ice sheets which increases sea level. Also causes water to expand further increasing sea level
- a decrease in temps cause more precipitation to fall as snow. This increases the volume of water stored in glaciers and so reduces the volume of the sea which decreases sea level

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5
Q

How does tectonic movement affect eustatic change?

A

Tectonic movements of the earths crust that alters the shape and volume of ocean basins
Eg sea floor spreading increasing the volume of the basin and so decreases sea level

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6
Q

What is isostatic sea level change caused by?

A

Vertical movements of the land relative to the sea

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7
Q

What does any downward movement of the land cause?

A

The sea to rise locally

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8
Q

What does the uplift of land cause the sea level to do?

A

Fall

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9
Q

The effects of isostatic sea level change local or global?

A

Always local

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10
Q

What are the 3 main causes of isostatic sea level change?

A

1) Uplift or depression of earths crust
2) subsidence of land
3) tectonic processes

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11
Q

How does uplift or depression of the earths crust affect isostatic sea level change?

A

Due to accumulation or melting of ice sheets. Slow uplift of land can continue for thousands of years after the weight of a retreating glacier has gone
Accumulation of sediment, mostly at mouths of major rivers can also cause depression

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12
Q

How does subsidence affect isostatic sea level change?

A

Subsidence of land due to shrinkage after abstraction of groundwater, eg drainage of marshland

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13
Q

How does tectonic processes affect isostatic sea level change?

A

Eg one plate is forced beneath another at a plate margin

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14
Q

How does sea level vary? On a yearly weekly or daily basis?

A

Daily basis with the tidal cycle

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15
Q

Onshore winds an atmospheric pressure systems also cause the sea surface to

A

Rise temporarily

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16
Q

How long ago was the last glacial period?

A

110,000 to 12,000 years ago

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17
Q

In the last glacial period how was water stored?

A

In ice sheets so sea level was lower than present

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18
Q

At the last glacial maximum (21000 years ago) how much lower was sea level?

A

130m lower

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19
Q

How long ago did temperatures melt ice sheets and raise sea levels to reach the present level?

A

4000 years ago

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20
Q

Over the last…… years sea level has fluctuated around its present value

A

4000

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21
Q

What year did sea levels start rising?

A

1930s ish

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22
Q

What is global warming?

A

Global temperatures rapidly increasing

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23
Q

There has been a sharp rise in average temperature of what between when and when

Study These Flashcards
A

1.08 degrees
1900 and 2016

24
Q

Why do scientists think climate change has increased so fast?

Study These Flashcards
A

Human activities

25
What do greenhouse gases do?
Absorb outgoing long- wave radiation so less is lost to space As there concentration increases, more energy is trapped and the planet warms up
26
Why does increase in temperatures cause an increase in sea levels?
Through melting of ice sheets and thermal expansion of water in oceans
27
How much is the global sea level currently rising at ?
2 mm per year
28
What is the predicted level of sea level growth rising predicted to be if the rate isn’t slowed?
8 to 16 mm a year by 2100
29
Changes in ocean circulation and wind patterns are likely to
Increase storms and make them more frequent and intense
30
If sea levels continue to rise like predicted what are four major impacts to the coastline it will have?
-More frequent and severe coastal flooding -Submergence of low lying islands -changes in the coastline -contamination of water sources and farmland
31
How will more frequent and severe coastal flooding impact coastal areas?
Already increase with sea level rise and will increase more with further rises. Eg from 1995 to 2004 kinds point in New York flooded 80 times but 2005 to 2016 nearly 160 times
32
How will submergence of low lying islands impact coastal areas?
Risk of disappearing If sea level rises by just 0.5m from current level most of the Maldives will be submerged
33
How does changes in the coastline impact coastal areas?
As sea levels rise the coastline changes- islands are created and the area of land is decreased Eg if sea level rises 0.3 m from current level 8000km^2 of land in Bangladesh will be lost
34
How does contamination of water sources and farmland impact coastal areas?
Salt water may enter bodies of fresh water near the coast damaging ecosystems and masking the water unsuitable for lots of uses Salt water entering soils may damage crops and make land impossible to farm
35
Sea level rise an increased storms will increase coastal erosion which
Puts ecosystems, homes and businesses at risk
36
What happens when sea levels fall relative to the coast?
New coastline emerges from the sea creating different landforms
37
What are landforms which are created as a result of sea level fall?
- raised beaches - wave cut platforms - relict cliffs
38
What are raised beaches?
Formed when the fall is sea level leaves beaches above the high tide mark. Over time beach sediment becomes vegetated and develops into soil
39
How does sea level fall expose wave cut platforms?
Leaves them raised above their former level
40
What are relict cliffs?
Cliffs above raised beaches are no longer eroded by the sea and slowly get covered in vegetation
41
What features are usually within relict cliffs?
Wave cut notches Caves Arches Stacks These raised features are degraded over time
42
Where are Rias formed?
Where river valleys are partially submerged
43
Characteristics of a Rias
Gentle long cross profile. Wide and deep at their mouth, become narrower and shallower the further inland they reach
44
What is a Fjord?
Drowned glacial valley
45
Characteristics of a Fjord
Relatively straight and narrow with very steep sides Shallow mouths caused by a raised bit of ground called the threshold Very deep further inland
46
How is a threshold formed and what is it?
Formed by deposition of material by the glacier Raised bit of ground
47
What is a Dalmatian coastline ?
An area where valleys lie parallel to the coast Increased in sea level forms a dalmation coastline
48
How do dalmation coastlines form?
Valleys are flooded leaving islands parallel to the coastline Named after the Dalmatian coast in Croatia
49
What are individual landforms?
Spits arches
50
What do individual landforms combine to create?
A landscape
51
Coastal landscapes can be dominated by processes of erosion or deposition but most are formed by
Both
52
Processes operating in coastal systems can create new landforms or change existing landforms what does this mean?
Coastal landscapes change over time
53
A change in one factor can lead to changes in others- give an example
Change in wave direction might increase deposition and eventually change a landscape dominated by erosive landforms to one dominated by depositional landforms
54
Relict landfoms can still experience coastal processes eg-
Relict cliff may be weathered by salt and freeze thaw
55
What are coastal landscapes made up of a mixture of?
Active and relict landforms that reflect different periods of change
56
Change can occur in a range of
Spatial and temporal scales
Beth- Physical Geography
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