3.a - emergent landscapes

Question 1

when do emergent coastal landscapes form?

Answer 1

as sea level falls

Question 2

what causes sea level change?

Answer 2

global temp ↑ = thermal expansion and ice sheets/glaciers melting = greater volume
climate change = extremes of weather - decrease in global temp = more precipitation falls as snow which turns into ice = ↓ vol of water in ocean = thermal contraction

Question 3

what landforms occur as a result of sea level fall?

Answer 3

emergent landforms

Question 4

what can eustatic change lead to?

Answer 4

coastlines being drowned/emerging from the sea

Question 5

what are 3 key factors coastlines are influenced by?

Answer 5

geology, relief and human activity

Question 6

when did the ice age happen and where was sea level in this time?

Answer 6

about 2 million years ago the world’s climate cooled and an ice age began that lasted until about 14,000yrs ago
during this Ice Age sea level was at least 120m lower than it is today

Question 6

how can earthquakes cause sea level change?

Answer 6

earthquakes can cause vertical movements either side of faults; this can lead to an apparent rise or fall in sea level at the coast

Question 7

how did the 2 different parts of Britain tilt?

Answer 7

during the ice age 2mill to 14,000 yrs ago, much of the British Isles was covered with ice to a line just north of London and Bristol, known as the Thames Severn line.
this additional weight on the crust pushed the northern part of the British Isles downwards (called compression), while the south, without the weight of the ice, rose slightly.
at the end of the ice age the loss of weight in the north led to the British Isles tilting the other way: Scotland and the North rose (isostatic rebound) while the south sank.
coastlines in scotland rose above sea level while coastlines in the south of england became submerged.

Question 8

what is eustatic change?

Answer 8

global changes in sea level due to changes in the atmosphere

Question 9

what is isostatic change?

Answer 9

localised/regional changes in sea level due to movements of the Earth’s crust

Question 10

what is the recent trend of global eustatic changes in sea level?

Answer 10

eustatic = worldwide rise in sea level from glaciers/ice sheets melting and global ↑ in temps. over last 6000 yrs = quite a lot os stability which leads to civilisation progressing and development

over the past 18,000 yrs change has been big - roughly 120m rise in sea level
sea level has risen at a linear rate as the Devension Ice melts

Question 11

what is the recent trend of isostatic changes in sea level around the UK?

Answer 11

isostatic = changes in the level of land due to ice melting.
- localised e.g Scotland.
- from tectonic activity (eqs)
- from removal/addition of weight from land

emergent Scotland/north.
- becomes risen above sea level = DECOMPRESSION/ISOSTATIC REBOUND

South/kent starting to become submergent.
- 3.5mm/yr change difference

Question 12

what is a long term natural reason for the changes in global temperature?

Answer 12

MILANKOVITCH CYCLES - most significant

variations in the earth’s orbit and tilt
he argued that long term climatic shifts (e.g. glacial cycles) are caused by astronomical events such as changes in the Earth’s axis and orbit and the precession of the equinoxes
these external forcing mechanisms affect the amount of solar radiation reaching the planet’s surface and its spacial/temporal distribution
they operate on time scales that vary from 10,000-100,000 yrs.
Milankovith identified climate cycles at 100,000, 43,000, 24,000 and 19,000 years, with long glacial periods followed by shorter interglacials

Question 13

what is the first short term natural reason for the changes in global temperature?

Answer 13

CHANGES IN SOLAR OUTPUT= 400yrs. only in past 30 yrs have satellites been able to measure solar irradience accurately
sun’s output varies over time
there is a positive correlation between the number of sunspots and solar energy outputs
solar output follows an 11 year cycle. the difference in energy output between max and min sunspot activity is ony 0.1% - not enough to impact global climate significantly
longer timescales = solar output is more variable
difficult to isolate the impacts of this from other influences

Question 14

what is the second short term natural reason for the changes in global temperature?

Answer 14

VOLCANIC ACTIVITY

eruptions = huge amounts of volcanic ash and sulphur dioxide into stratosphere = potential to change the climate
sulphur dioxide has a cooling effect and is more persistent. in atmosphere it is converted to sulphuric acid = sulphate aerosols
these reflect solar radiaton back into space and lower temps in the troposphere

Question 15

what are emergent features affected by?

Answer 15

after their emergence, these landforms were no longer affected by wave processes
however, they continure to be affected by weathering and mass movement

Question 16

what is a raised beach?

Answer 16

areas of former shore platforms that are left at a higher level than the present sea level
they are often found a distance inland from the present coastline.
behind the beach along emergent coastlines it is not uncommon to find abandoned cliffs w/ wave cut notches, cave and even arches and stacks.
depositis are likely still sand and pebbles

Question 17

what is a marine terrace?

Answer 17

much larger scale landscape features than raised beaches which are quite small scale and localised at the base of relic cliffs
terraces don’t necessarily have cliffs above them
their formation is essentially the same as raised beaches - marine erosion during a previous period of higher sea level
found as far as 50m higher up than raised beaches

Question 18

what is a relict cliff?

Answer 18

there is a sharp rise in the level of the land that marks the position of former coastal cliffs; now known as relic cliffs
found behind the raised beach/marine terrace

Question 19

what current processes could be modifying emergent landforms today?

Answer 19

landforms aren’t affected by marine/wave processes yet are affected by weathering and mass movements
cliffs arent undermined = slope will decrease in gradient and are far more stable
people pressure and footpath erosion will alter landforms
relic cliffs may become vegetated

Question 20

what do emergent coastlines represent?

Answer 20

coastlines that are now raised above present day sea-level.
this means the coastline has experienced a relative fall in sea-level (marine regression)

Question 21

where do emergent coastlines originate?

Answer 21

such coastlines may have 2 origins:
they may have formed at times when eustatic sea-level was higher, for example, during warmer interglacial periods
they may have formed and become lifted by isostatic rebound. this is when there is a relative rise of the land above present day sea levels (e.g Scotland)