Coastal landforms evolve as climate changes

Question 1

Climate change & the resultant sea-level FALL.

Answer 1

TYRRHENIAN INTER-GLACIAL PERIOD:
- 130,000 years ago, global mean annual temperatures were almost 3 degrees higher than today.

• This caused sea levels to be about 20m above todays position.

RISS GLACIAL PERIOD:
- 108,000 temperatures fell 7 degrees lower than today.
- sea levels dropped by over 100m , making them about 83m lower than the present day.

Caused the formation of EMERGENT landforms.

Question 2

Reason for the sea level reduction

Answer 2

• A decrease in global temperature leads to more precipitation in the form of snow.
• The snow turns to ice and so water is stored in its solid form on land rather than being returned to the ocean store as a liquid.
• This results in the reduction in the volume of water in the ocean store and a world wide fall in sea level.
• Also, water molecules CONTRACT leading to an INCREASED density and a REDUCED volume.

Question 3

Raised beach- emergent

Answer 3

• Areas of former shore platforms that are found at a HIGHER LEVEL than the present SEA LEVEL.
• They are often found a distance INLAND from the present coastline.

Question 4

Abandoned cliff - emergent

Answer 4

• Usually found behind a beach , along EMERGENT coastlines.
• During inter-glacial periods, sea levels were much higher, meaning higher EROSION rates.
• This is due to deep water allowing GREATER wave energy due to less FRICTION with the sea - floor.
• This caused the formation of many erosional landforms including wave-cut notches , caves , stacks and stumps.
• wave erosion also occurred at high elevations forming active cliffs and shore platforms.
• When sea levels FELL during the next glacial period , these landforms were left behind , FURTHER INLAND of the new, lower sea-level position.

Question 5

Marine terraces emergent

Answer 5

• When sea levels fall in STAGES
• Marine erosion is able to develop a number of marine terraces, appearing as steps in the landscape.
• Each step represents a period of STABLE temperatures and sea level.
• Wave action had sufficient time to act significantly on the landscape to produce a FLAT, eroded terrace.
• These are a result of DECREASING sea levels or RISING land levels.

Question 6

EMERGENT landform modification

Answer 6

• After emergence , these landforms are no longer affected by wave processes, but instead by WEATHERING & MASS MOVEMENT.
• Post-glacial period, the conditions were WARM and WET leading to vegetation growing on these landforms making them difficult to recognise.
• Warmer conditions are predicted for the future, which will increase chemical weathering and mass movement, leading to continued DEGRADATION.
• If temperatures increase sufficiently , sea levels could rise so much , that these emergent landforms find themselves closer to or even at the coastline.
• This means they will return to being affected by WAVE PROCESSES.

Question 7

Sea level change

Answer 7

EUSTATIC - A GLOBAL change in sea level resulting from an actual fall or rise in the level of SEA.

ISOSTATIC - A LOCAL change in sea level resulting from the LAND rising or falling relative to the sea.

Question 8

Climate change and the resultant sea-level RISE

Answer 8

• An increase in global temperatures leads to higher rates of MELTING of ice stores.
• This increases the global volume of water in the ocean store resulting in sea level rise.
• temperature increase, also leads to water molecules EXPANDING, also increasing the volume.
• A ONE DEGREE CELCIUS increase in temperature causes a TWO METRE rise in sea level.

WURM GLACIAL PERIOD:
- 25,000 years ago, temperature were 9 degrees lower than today and sea levels were 90 metres lower.

• Since then, temperatures and sea level has risen , known as the FLANDRIAN TRANSGRESSION.

Question 9

Rias - Submergent

Answer 9

• SUBMERGED RIVER VALLEYS, formed as sea level rises due to climate increase.
• In plan view , they are often winding, reflecting the original route of the channel and its valley sides, formed by fluvial erosion within the channel and sub - aerial processes on the valley sides.
• Often filled with sediment deposits that were eroded by flowing rivers that moved down the channel in earlier periods.
• In interglacial periods, deposition would have continued as sea level rose and the flow of the river slowed , depositing material.

EXAMPLE:
- SOUTH coast of Devon and Cornwall.
- Formed during the POST-GLACIAL sea level rise of the FLANDRIAN TRANSGRESSION.

Question 10

Fjords - Submergent

Answer 10

• SUBMERGED GLACIAL VALLEYS.
• Steep, cliff -like valley sides
• Water is UNIFORMLY deep , reaching over 1000m.
• CROSS SECTION is U shaped reflecting the original shape of the glacial valley itself.
• Have a GLACIAL ROCK BASIN with a shallower section called the THRESHOLD.
• This results from LOWER rates of erosion at the SEAWARD end of the valley where the ICE THINNED in warmer conditions.
• STRAIGHTER PLANFORMS as the glacier would have TRUNCATED (shortened) any INTERLOCKING SPURS.
• Further deepened by MARINE EROSION due to extensive depth.

EXAMPLE:
The Sogne Fjord ~ Norway, almost 200km long.

Question 11

Shingle Beaches - Submergent

Answer 11

• when sea level FALLS , large areas of new land EMERGES from the sea.
• SEDIMENT accumulates on this surface , deposited by rivers and low-energy waves.
• At the end of the last glacial period, sea level rose .
• This caused WAVE ACTION to push these sediments ONSHORE.
• In some places they were deposited at the base of former CLIFF lines , elsewhere they form TOMBOLOS and BARS.

Question 12

SUBMERGENT landform modification

Answer 12

Sea levels are predicted to rise by a further 0.6m in the next 100 years.

RIAS & FJORDS:
- cause the water depth of these to increase.
- increased MARINE EROSION as they are more likely to face stormier conditions and larger waves.

SHINGLE BEACHES:
Vulnerable to modification as they are composed of UNCONSOLIDATED rock material rather than solid rock.