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Coastal Landscapes > 3.a. Emergent coastal landscapes form as sea level falls. > Flashcards

3.a. Emergent coastal landscapes form as sea level falls. Flashcards

1
Q

What is eustatic sea level change?

A

The rise, fall and overall volume of water in the oceans.

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2
Q

What is eustatic sea level change heavily influenced by? Why?

A

Temperatures, as it reduces water density.

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3
Q

When does eustatic change take place?

A

During and after a glacial period.

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4
Q

At the start of a glacial period, the temperature falls. How does this affect water? What does this do to sea levels?

A

This allows water to be frozen and stored in glaciers inland.

This results in water being taken out of the sea but not being put back in leading to an overall fall in sea level.

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5
Q

As a glacial period ends, what happens to temperatures? How does this affect water and sea levels?

A

Temperature begins to rise.

This means the water stored in the glaciers will replenished the sea, increasing sea levels.

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6
Q

What is isostatic sea level change?

A

The changing level of the land.

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7
Q

What is isostatic rebound?

A

The process by which large ice sheets cause subsidence and uplift when they melt.

E.g. Scotland rises back up, and Southern England falls back down.

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8
Q

Global temperatures melt what? How does this sea levels? What does this cause?

A

Ice caps, ice sheets, and glaciers.

This means more water is in the ocean.

This results in lower temperatures, meaning more ice on land.

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9
Q

Outline the Riss glacial period.

A

108,000 years ago.

Global mean annual temperatures were ~7°C lower than those today.

Sea level was less than 83m below present position.

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10
Q

Outline the Tyrrhenian inter-glacial period.

A

130,000 years ago.

Global mean annual temperatures were ~3°C higher than those today.

Sea level was 20m above present position.

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11
Q

Outline process from the start of the Tyrrhenian interglacial period, to the Riss glacial period.

A

130,000 years ago, was the start of the Tyrrhenian inter-glacial period.

Global mean annual temperatures were almost 3°C higher than today.

Sea level was about 20 m above today’s position.

20,000 years later began the Riss glacial period.

Temperatures fell, reaching a minimum about 7°C lower than today/

As a result, less water was returned to the ocean store and sea levels dropped by over 100 m, (83 m lower than the present day).

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12
Q

Global temperatures decreases lead to what? What does this allow? What does this result in?

A

More snow precipitation.

This allows water and ice to be stored on land in solid form (rather in the ocean as a liquid).

This results in a reduction of global sea levels (and volume of water in ocean stores).

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13
Q

It is estimated that a 1°C fall in mean global temperature causes sea level to fall approximately how many metres?

A

Approximately 2 m.

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14
Q

High sea levels = …

A

Higher global annual temperatures.

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15
Q

Lower sea levels = …

A

Lower global annual temperatures.

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16
Q

What are the three Milankovitch cycles?

(Natural Causes of Climate Change)

A

Eccentricity.

Procession.

Axial Tilt.

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17
Q

What is eccentricity?

(Eccentricity)
(Natural Causes of Climate Change)

A

The change in the Earth’s orbit, circular to elliptical.

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18
Q

How do circular orbits change the climate?

(Eccentricity)
(Natural Causes of Climate Change)

A

By bringing mild winters and warm summers.

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19
Q

How do elliptical orbits change the climate?

(Eccentricity)
(Natural Causes of Climate Change)

A

By bringing long harsh winters.

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20
Q

How often do eccentricity changes occur?

(Eccentricity)
(Natural Causes of Climate Change)

A

400,000 year cycle.

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21
Q

Why does eccentricity cause climate changes?

(Eccentricity)
(Natural Causes of Climate Change)

A

When the Earth’s orbit is more elongated, it receives more energy from the sun, than when the orbit is circular.

22
Q

What is procession?

(Procession)
(Natural Causes of Climate Change)

A

The idea that when the Earth rotates, it wobbles slightly upon its axis.

23
Q

How often do procession cycles occur?

(Procession)
(Natural Causes of Climate Change)

A

On a 26,000 year cycle.

24
Q

How does procession change the climates?

(Procession)
(Natural Causes of Climate Change)

A

Makes seasonal contrasts more extreme in one hemisphere and less extreme in the other.

25
Q

What is axial tilt?

(Axial tilt)
(Natural Causes of Climate Change)

A

The idea that the tilt of the Earth’s axis varies between 22.2° and 24.5°.

26
Q

How often does axial tilt occur?

(Axial tilt)
(Natural Causes of Climate Change)

A

On a 41,000 year cycle.

27
Q

The greater the axial tilt, the…

(Axial tilt)
(Natural Causes of Climate Change)

A

More solar energy the poles receive.

28
Q

How does solar activity affect the climate?

(Solar activity)
(Natural Causes of Climate Change)

A

Every 11 years there are variations in solar radiation.

29
Q

How does volcanic activity affect the climate - short-term?

(Volcanic activity)
(Natural Causes of Climate Change)

A

Ash clouds block the sun.

30
Q

How does volcanic activity affect the climate - long-term?

(Volcanic activity)
(Natural Causes of Climate Change)

A

Sulphur dioxide acts like tiny mirrors, reflecting radiation back towards Earth, stopping it from leaving.

31
Q

When are emergent landforms formed?

A

During Eustatic sea level fall.

32
Q

What shaped emergent landforms?

A

Wave processes when sea level was higher.

33
Q

Where are emergent landforms found?

A

In-land, away from the coastline, (~100m away).

34
Q

What are raised beaches?

(Raised beaches and abandoned cliffs)

A

Areas of former shore platforms that are left at a higher level than the present sea level.

35
Q

Where are raised beaches often found?

(Raised beaches and abandoned cliffs)

A

A distance inland from the present coastline.

36
Q

What do abandoned cliffs often feature?

(Raised beaches and abandoned cliffs)

A

Wave-cut notches, caves, and even arches and stacks.

36
Q

Where are abandoned cliffs often found?

(Raised beaches and abandoned cliffs)

A

Behind raised beaches.

37
Q

What are marine terraces? Where are they found?

(Marine terraces)

A

Much larger scale landscape features than raised beaches, which are quite small scale and localised at the base of relic cliffs.

38
Q

Marine terraces act over a much longer time scale than raised beaches? What does this mean for its structure?

(Marine terraces)

A

They tend to be substantially larger in extent.

39
Q

Do marine terraces always feature abandoned cliffs above them?

(Marine terraces)

A

No.

40
Q

How are marine terraces formed?

(Marine terraces)

A

Marine erosion during a previous period of higher sea level.

(Essentially the same as raised beaches).

41
Q

Give an example of a raised beach/ abandoned cliff/ marine terrace. How far above present day sea level are the features? When were they formed?

(Raised beaches, abandoned cliffs, and marine terraces)

A

The Southern tip of the Isle of Portland near Weymouth in Dorset.

15 m above the present day sea level.

Formed around 125,000 years ago during the Tyrrhenian inter-glacial period.

42
Q

If temperatures increase sufficiently, what does this cause? What can this lead to? What would happen as a result of this?

(Wave processes)
(Peri-glacial Modifications of Emergent Landforms)

A

Eustatic sea level rise.

This could lead to these emergent landforms being found much closer to the coastline.

They would then be subjected to wave processes and modification once more.

43
Q

Cryoturbation takes place over how long? How long are its cycles?

(Cryoturbation)
(Peri-glacial Modifications of Emergent Landforms)

A

Takes place over millennia, occurring in 9 month cycles.

44
Q

What happens to soils in the summer, and in the winter? How does this affect abandoned cliffs?

(Cryoturbation)
(Peri-glacial Modifications of Emergent Landforms)

A

Soils thaw in the summer and freeze in the winter.

This weakens the cliff, and joints and faults widen; breaking down the internal geological structures of the abandoned cliff, producing regolith.

45
Q

Give an example of cryoturbation.

(Cryoturbation)
(Peri-glacial Modifications of Emergent Landforms)

A

Isle of Portland’s contortions in fragmented limestone.

This is a result of freezing and thawing of the permafrost in the subsoil during the late Pleistocene period.

46
Q

After emergence, landforms are no longer effected by wave processes. What modifies them instead?

(Post-glacial Modifications of Emergent Landforms)

A

Weathering and mass movement.

47
Q

What happens to cliff faces during free-thaw weathering?

(Physical weathering and mass movement)
(Post-glacial Modifications of Emergent Landforms)

A

They are gradually degraded.

This causes rock falls from the cliff face.

48
Q

How will climate change impact chemical weathering?

(Chemical weathering and mass movement)
(Post-glacial Modifications of Emergent Landforms)

A

Cause chemical weathering to become more influential (Van’t Hoff’s law), especially by carbonation of limestone cliffs and platforms.

49
Q

Climate change will cause chemical weathering to become more influential. What will this increase as a result?

(Chemical weathering and mass movement)
(Post-glacial Modifications of Emergent Landforms)

A

Increase the speed at which mass movement processes occur, once physical weathering has exposed underlain rock.

50
Q

Climate change may be significant for biological weathering at raised beaches. Why?

(Biological weathering and mass movement)
(Post-glacial Modifications of Emergent Landforms)

A

Colonisation of the surface, through the increasing numbers of marine organisms, e.g. whelks.

51
Q

Outline how tree roots on cliffs can weather abandoned cliffs.

(Biological weathering and mass movement)
(Post-glacial Modifications of Emergent Landforms)

A

Tree roots on top of cliffs are very significant in exerting leverage on rocks and soil when they topple - having the potential to trigger rock falls.

Coastal Landscapes (9 decks)

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