COASTS AND PHYSICAL SYSTEMS Flashcards
Contribution of marine processes in the development of landforms (6)
AO1
Transportation and deposition processes produce distinctive coastal landforms (beaches, recurved and double spits, offshore bars, barrier beaches and bars, tombolos and cuspate forelands), which can be
stabilised by plant succession.
Sediment transportation is influenced by the angle of wave attack, tides and currents and the process of longshore drift.
Vegetation is important in stabilising sandy coastlines through dune successional development on sandy coastlines and salt marsh successional development in estuarine areas.
Need to relate to source booklet!
Contribution of subaerial processes in the development of landforms (6)
Subaerial processes of mass movement and weathering influence
coastal landforms and contribute to coastal landscapes.
Weathering (mechanical, chemical, biological) and mass movement
(blockfall, rotational slumping, landslides) is important on some coasts
with weak and/or complex geology.
Mass movement creates distinctive landforms (rotational scars, talus
scree slopes, terraced cliff profiles).
Need to relate to booklet!
Explain the role of sea level change in the formation of both emergent and submergent coastlines (8)
Emergent coastlines are formed with falling sea level relative to land due to isostatic change creating features such as raised beaches and fossil cliffs such as those found at Ullapool in Scotland.
A beach and cliff well above the contemporary sea level were created when the sea level was much higher. As the sea level has dropped, it has left a fossil cliff and sediment as a raised beach as well as a contemporary cliff and beach which reflects the current sea level.
Coastline of submergence are formed with rising sea levels creating features such as rias and fjords. As sea level appears to rise in places such as SW England, Rias such as the river Dart are created when rising sea level drowns a previous river valley. In cross section the ria is relatively shallow with the deepest part in the centre. The exposed
valley sides are gently sloping. There is a smooth long profile and in plan view tend to be winding as they reflect the course of the drowned river.
Fjords are created when the very deep coastal glacial U shaped valleys called glacial troughs are flooded by rising sea levels. Fjords have steep valley sides and uniformly deep water (1000m) with a U shaped cross section reflecting the glaciated valley. There is often a
shallow section at the mouth of the Fjord known as the threshold. In plan view they are much straighter due to the erosive power of the glacier.
Sea level change has also created Dalmatian coasts. This is where there is a longitudinal coast where mountains run parallel or
concordant to the coast. The name is taken from the coast of Dalmatia, where the submergence of the coastline produces long, narrow inlets with a chain of islands
parallel to the coast. As sea levels rose they flooded the elongated islands are the crests of former ranges and the narrow sounds were the former longitudinal valleys.
Evaluate the view that global warming is the greatest threat to coastlines and their communities (20)
A01:
Climate change may increase coastal flood risk (frequency and magnitude of storms, sea level rise) but the pace and magnitude of this threat is uncertain. Storm surge events can lead to severe coastal flooding with dramatic short-term impacts (depressions, tropical cyclones).
Local factors increase flood risk on some low-lying and estuarine coasts (height, degree of subsidence, vegetation removal)
Rapid coastal recession is caused by physical factors (geological and marine) but can be influenced by human actions (dredging or coastal management)
Rates of recession are not constant and are influenced by different factors both short- and longer term (wind direction/fetch, tides, seasons, weather systems and occurrence of storms
Suggest one reason for the differences in the growth of electricity generated from solar power (3)
The EU has seen a smaller / slower growth rate electricity generated from solar power from (98000 to 131000 mw)
This may be due to EU countries prioritizing other renewable resources such as wind power which may be
more reliable
Explain how oceans regulate the composition of the atmosphere (6)
“How do oceans help control the gases in the air?”
The oceans regulate the composition of the atmosphere due to it’s ability to be a vital flux as the oceans absorb carbon dioxide into the surface ocean store (900 GtC) through the process of diffusion (90GtC per year). Crucially, as the oceans can absorb more carbon than it emits (a net gain of 0.6 Gtc yr-1), this means that it is considered a carbon sink and so highlights the importance of the oceans in regulating the composition of the atmosphere.
Crucially, there are three key processes that occur in oceans that allows them to be a carbon sink with the atmosphere – a physical, solubility and biological cycle.
Physical pump /Thermohaline circulation:
The most important is the physical pump.
The physical cycle is caused when carbon dioxide is absorbed by the ocean surface through the process of diffusion. This can be then dissolved into the surface ocean and then is taken from the surface ocean to the intermediate and deep oceans through downwelling currents (96 GtC per year). It is also distributed around the planet through the thermohaline circulation. This is the process whereby warm water from the tropics
is transported towards the poles. As the colder the water the greater the absorption of CO2 this means that as warm water is transported towards the poles it cools absorbing more CO2. As it does so the
salinity also increases and as a results it sinks (down welling) taking CO2 from the surface ocean to the deep ocean. This therefore removes carbon from the upper ocean and removes to the deep ocean. This allows more diffusion to occur regulating the carbon store
in the atmosphere.
Yet there is also the upwelling of carbon from intermediate and deep oceans to the surface oceans (105.6 GtC yr-1) through upwelling currents and turbulence created by surface winds allowing carbon
previously stored in the intermediate and deep ocean store to return to the surface oceans and then back to the atmosphere highlighting that the role of oceans in regulating the carbon cycle in the atmosphere is a two way relationship with carbon being moved both downwards and upwards through the oceans.
Biological cycle /Sequestration of carbon through photosynthesis: The next important is the biological pump. The biological cycle allows carbon dioxide to be sequestered in the ocean through photosynthesis by phytoplankton and other marine biota which converts the carbon dioxide into organic matter (10GtC per year). This then acts as a biological pump transporting carbon from the surface oceans to the intermediate and deep oceans (10 GtC per year). This occurs when
as these biological organisms die, their dead cells, shells and other parts sink into the mid and deep water. In addition, decay of these organism also releases carbon dioxide into this intermediate and deep water. Thus the oceans role in regulating the composition of the atmosphere is that it moves carbon from the surface oceans where it may vent back into the atmosphere and instead store it the mid and deep ocean store as well as the dissolved carbon store and so regulate the carbon cycle.
Solubility cycle/Carbonate pump
The solubility cycle also is a key process in the oceans.
The solubility cycle is caused when the carbon dioxide absorbed by the oceans from the atmosphere forms carbonic acid which in turn reacts with hydrogen ions to form bicarbonates and then further reactions forms carbonates which are stored in the upper ocean. Some organisms use these carbonates to make shells or skeletons. When these organisms die some material sinks right to the bottom of the ocean and forms the sea bed sediment store (1750 GtC) where over time through chemical and physical processes the carbon is transformed to rocks such as limestone. This is a particularly important process in regulating the composition of the atmosphere as it locks up carbon in the long term carbon cycle and not allows it to return to the ocean surface and so possible venting into the atmosphere as the physical pump does.
Explain the contribution of human activity to the risk of drought (8)
Humans contribute to the risk of drought through overabstraction of both surface and ground water stores. In the Sahel region water hungry crops such as ground nuts were grown and cattle herd sizes
increased as more wells were dug. As a result of the increase in the number of wells the ground water levels started to fall. This fall in ground water levels was then accelerated by the drop in rainfall associated with the failure of the ITCZ. This meant that there were
too many cattle and not enough ground water to meet this demand and so the area suffered from drought both in the 1970’s and in 2005.
In addition the risk of drought can be caused by rapid population growth. Sahelian countries such as Niger were experiencing a population explosion with fertility rates of 7 per women and a growth rate of over 3% per year. This also contributed to the risk of drought.
Deforestation can add to the risk of drought as removing trees can break the cycle of precipitation/interception and subsequent
evapotranspiration leading to lower precipitation levels and so drought.
The development of dams and reservoirs can cause drought downstream such as the Ataturk Dam in Turkey and the impacts on
downstream countries such as Syria and Iraq as well as the series of dams in the Colorado drainage basin leading to drought in Mexico.
Yet human activity is often seen as only exacerbating lower than usual levels of precipitation leading to drought. The risk of drought can also be therefore be thought of being caused by meteorological processes such as the ENSO cycle in Australia leading to events such as the Big Dry as well as hydrological processes such as the low levels of winter precipitation levels leading to the drought orders in the UK in the
Spring of 2012.
Assess how successful different countries have been in achieving energy security (12)
Evaluate the view that land use changes are the main cause of the increasing risk
of river flooding (20)
Explain why there are uncertainties about future levels of carbon release from peatlands and permafrost (8 marks)
Relevant points may include:
AO 1
* Permafrost covers some 25% of the exposed land cover in the Northern Hemisphere and contains 1672Gtc of carbon which is not usually considered
in carbon cycle models.
* There is an uncertainty over how much the permafrost has warmed with estimates varying between 0.5oC and 2oC as a result of differences in study regions giving different estimates.
* There are also uncertainties over future changes with estimates varying from 2.8oC to 7.8oC mainly as a result of the uncertainties of the rate of industrialisation in HMHD.
* There are also uncertainties over the spatial loss of permafrost with estimates varying from 7% to 88% as there are uncertainties as we don’t know the extent to which global treaties such as the Paris agreement will reduce emissions.
* There are also uncertainties over the increases in the depth of the active layer with estimates varying from an increase of 40% to 100%. The greater the increase the greater the emissions of carbon as there are uncertainties as we are unsure of the feedback mechanisms between future changes in climate and carbon release from permafrost.
* There are also uncertainties over the role of talik formation, thermokarst development and the rate of river and coastal erosion all of which will cause
variations in carbon emissions from permafrost areas.
* The burning, draining and degrading of peatlands emits more than one tenth of the global emissions released from burning fossil fuels.
* There are also uncertainties over the rate of restoration of peatlands which will reduce carbon emissions from these sources. Degraded peatlands can be restored.
* Crucially it is uncertain the extent to which the drainage of peatlands will be reduced.
Assess the role of physical factors in influencing the pattern of future water stress (12 marks)
Relevant points may include:
AO1
* The growing mismatch between water supply and demand has led to a
global pattern of water stress (below 1,700 m³ per person).
* The causes are physical such as climate variability and salt water
encroachment at coast.
* The finite water resource faces pressure from rising demand (increasing
population, improving living standards, industrialisation and agriculture),
which is increasingly serious in some locations.
* The causes are human such as over abstraction from rivers, lakes and
groundwater aquifers, water contamination from agriculture, industrial
water pollution.
AO2
* A physical factor is the climate as some areas will have water stress as
people are living in arid areas such as Saudi Arabia will have very high levels
of projected water stress as they are underneath the descending arm of the
Hadley Cell.
* Semi-arid areas will have a high level of projected water stress such as the
US and Mexico (High) as well as Australia.
* Areas on the equator such as Nigeria will continue to have a high
precipitation level and so a low level of projected water stress.
* The distribution of precipitation over the year will also cause projected high
level of water stress. Areas with ephemeral rivers where rivers only flow in
winter months leading to water shortages in the summer such as Tunisia.
* The geology of the country also plays a role as countries such as the UK
which has many aquifers such as the South Downs will have a lower
projected water stress than similar climatic areas such as Belgium which do
not have the same ground water supplies.
* Climate change is likely to reduce precipitation levels - which may be making
the water situation worse in some areas such as Pakistan which is projected
to have a very high level of water stress.
* Another key physical factor are where there are transboundary sources
where some area which have a projected very high water stress are areas
such as Syria and Israel which rely upon transboundary water sources.
* There are also human factor that influence the pattern of projected water
stress. Areas with rapid population growth such as India have a high level of
projected water stress when the development of water supplies does not
match the increase in population.
* Areas that are undergoing rapid economic growth such as China have a high
projected level of water stress industries require more water and as the
wealth of the population rises, the demand for domestic water also
increases.
* Overuse due to high levels of economic wealth can also cause high levels of
projected water stress as in wealthy countries, the demand for domestic
use is rising as is demand for agriculture are people want more expensive
‘succulent fruit and vegetables. As a result water stress in Southern Europe
is increasing such as in Spain.
* The map clearly shows that although human factors do play a significant
role in some areas where there is either rapid population growth or
economic development, physical factors play perhaps the more significant
role as areas with high levels of precipitation are still projected to have low
levels of water stress regardless of economic development or population
growth.
Evaluate the view that large-scale water management projects often create more problems than they solve for people and the environment (20 marks)
Relevant points may include:
AO1
* The pros and cons of the techno-fix of hard engineering schemes to include
water transfers, mega dams and desalination plants.
* Large scale water management projects can also include national projects at
a household level such as the provision of grey water systems or pumpkin
tanks.
* Integrated drainage basin management for large rivers are always
controversial.
* The potential for conflicts to occur between users within a country, and
internationally over local and trans-boundary water sources
* Water frameworks (United Nations Economic Commission for Europe
(UNECE), Water Convention, Helsinki, and the Water Framework Directive
and Hydropower, Berlin).
AO2
* An advantage of the development of large scale water management
schemes such as mega dams is that they reduce the flood risk and so allow
the river to be used as transport artery. This can also aid regional
development as is the case in the development of Wuhan on the Yangtze
PMT PMT
which has developed partly as the result of the Three Gorges dam regulating
the flow of the river.
* Large scale water management schemes can also displace large numbers of
residents (1.2m in the case of the Three Gorges dam) due to the creation of
reservoirs therefore creating conflict between the local people and (often)
other users in urban areas.
* Large scale water management schemes also can creates HEP which helps
develop the region and country and even, in the case of the Gibe III dam
create a source of foreign revenue as the electricity can be exported to
neighbouring (richer) countries.
* Such schemes also often disrupt the hydrology of rivers and there are often
irreversible changes downstream resulting in other users losing access to
ancient fishing grounds such as in Ethiopia as well as damage to ecosystems
such as the loss of the river Yangtze Dolphin.
* Another advantage of large scale water management schemes such as mega
dams is that they provide water for agriculture, industry and people.
Schemes such as in the Colorado Drainage basin provide water for millions
of people in cities such as Phoenix and Las Vegas as well as irrigating large
areas of crops in the Imperial Valley.
* Water transfer schemes can also provide water for irrigation creating both
regional and national advantages such as the Snowy mountain scheme in
Australia and the water transfers associated with the Aral Sea in Uzbekistan.
* Yet these schemes often alter the water quality and cause conflicts with
downstream users who can no longer utilise the resource such as those
farmers on the River Colorado in Mexico as well as destroying ecosystems
such as the delta of the river Colorado.
* Water treaties can reduce some of these problems caused by the
development of large scale water management schemes. The IWBC signed
between the US and Mexico has reduced the problems caused by the
developments on the river Colorado and the Mekong River Commission has
also reduced the problems found in the lower basin of the Mekong River.
* Water is a finite resource and it is therefore very likely that in almost all
cases large scale water management schemes will create both advantages
and cause problems.
* Problems can be reduced but not eliminated through the use of water
treaties and frameworks but these too are at the mercy of asymmetrical
power relationships. In terms of the environment, however, it is likely that
there are more problems caused as the purpose of the large scale projects is
to provide water for people rather than enhance the environment.
Explain the role of isostatic processes in causing changes in relative sea level (6 marks)
Relevant points may include:
AO1
* Longer-term sea level changes result from a complex interplay of factors
both eustatic (ice formation/melting, thermal changes) and isostatic (post
glacial adjustment, subsidence, accretion) and tectonics.
* Sea level change has produced emergent and submergent coastlines .
* Contemporary sea level change from global warming or tectonic activity is a
risk to some coastlines.
AO2
* The map shows a varied pattern of sea level change but there is some
evidence to suggest that the south of the British Isles are experiencing
relative sea level rise whilst the north of the British Isles are experiencing
relative sea level fall.
* isostatic changes refers to when crustal material is forced down into the
mantle changing the relative sea level.
* In particular the resource shows that it is likely that post glacial adjustment is
causing Scotland to be rebounding upwards and so relative sea levels have
fallen in Scotland leading to the sea level falls noted in the resource.
* It is also likely to be adding to the relative sea level rise experienced in the
south of England.
* It is also likely that subsidence/accretion is also contributing to the changes
shown with large river such as the Thames increasing the accumulation of
sediment in the Thames basin causing the land to subside into the mantle
causing relative sea levels to rise.
Evaluate the view that rates of coastal recession are largely controlled by geological factors (20 marks)
Relevant points may include:
AO1
* Bedrock lithology (igneous, sedimentary, metamorphic) and unconsolidated
material geology are important in understanding rates of coastal recession.
* Differential erosion of alternating strata in cliffs (permeable/impermeable,
resistant/less resistant) produces complex cliff profiles and influences
recession rates.
* Geological structure (jointing, dip, faulting, folding) is an important influence
on coastal morphology and erosion rates, and also on the formation of cliff
profiles and the occurrence of micro-features, e.g. caves.
* Weathering (mechanical, chemical, biological) is important in sediment
production and influences rates of recession whilst mass movement
(blockfall, rotational slumping, landslides) is important on some coasts with
weak and/or complex geology.
* Different wave types (constructive/destructive) influence beach morphology
and beach sediment profiles.
AO2
* Geological factors can refer to lithology, geological structure as well as
geological strata.
* Lithology refers to the physical characteristics such as colour, texture, grain
size, or composition.
* Sedimentary rocks such as chalk, limestone, sandstones and clays are rocks
which are created by the deposition of sediments. They generally are not
resistant to coastal recession.
* Igneous rock such as granite and basalt are formed through the cooling of
magma either above ground (basalt) or below ground (granite). They are more resistant to erosion than sedimentary rocks but often have lines of
weakness called joints created during the cooling process which can create opportunities for both marine and sub aerial processes.
* Metamorphic rocks are those sedimentary and igneous rock which are
deformed through heat and pressure to form new rocks – ie Clay to Slate, granite to gneiss. These are the most resistant to coastal recession as they
do not have bedding planes such as sedimentary rock and rarely have joints as igneous rocks.
* Unconsolidated material are formed in the Quaternary geologic era and
consist of Pleistocene and Holocene deposits. These are very susceptible to
coastal recession as seen on the Holderness coast and in North Norfolk.
* Geological structure refers to the changes to rocks brought about by stress
and strain such as jointing, dip, folding and faulting. All of these processes
create weaknesses in the rock which makes them more susceptible to
coastal recession.
* As well as the bedrock lithology being a key factor in influencing coastal
recession rates, alternating strata in cliffs also influences recession rates.
This is where one rock type rests on another. Knock Cliff on the Isle of Wight
has a rapid rate of cliff retreat as a result of a layer of permeable rock
overlying a layer of impermeable gault clay. When it rains water percolates
through the sandrock but cannot percolate through the gault clay. As a
result there is a lubrication slip plain created between the two rocks which
leads to rotational slumping and so a high rate of coastal recession.
* Wave type can also be key. There are two main wave types – destructive and
constructive. Destructive waves such as those at Freshwater Bay have High
wave height a short wave length and often produce plunging breakers where
the backwash is greater than the swash. This all means that areas that
receive destructive waves will have a higher rate of coastal recession than
those that receive mainly constructive waves.
* Wave size is also important. Large waves have more destructive power if
they have a long fetch, are generated in large water bodies, are formed by
strong prevailing wind and are not interfered with by other wave patterns.
On the IOW, Freshwater Bay and Compton Bay are exposed to the full fury of
the waves generated by the prevailing SW winds. The potential fetch
reaches the USA and there is little interference from other wave patterns.
This makes the erosive capabilities of the waves particularly strong at both of
these locations. At Sandown Bay the bay is sheltered by the cliffs at Knock
Cliff and as a result the waves have far less power leading to lower rates of
coastal recession.
* A beach is the most effective way to dissipate the energy of waves. Where
there is no beach and the waves impact directly upon the shore there can be
far higher rates of coastal recession than where there is a beach.
* Conversely deep water can cause clapotis – where the waves hit the cliff face
without breaking as the depth of water is too great. This then reflects the
wave back out to sea and as a result there are often low levels of coastal
recession.
* As well as physical processes effecting the rate of coastal recession there are
also human factors. The building of offshore breakwaters, the beach
renourishment and other cliff foot defences at Monks Bay has reduced the
coastal recession being suffered at this part of the Undercliff, but the
construction of a sea wall at the extreme eastern end has merely deflected
the erosive power of the sea to Steel Bay where there has been considerable
land slipping.
Explain how the physical features of a drainage basin affect the shape of storm hydrographs.
You may draw a diagram to help your answer. (6 marks)
Relevant points may include:
* Storm hydrographs shape depends on physical features of drainage basins
(size, shape, drainage density, rock type, soil, relief and vegetation)
* The key shapes of the hydrograph are the steepness of the rising limb, the
nature of the peak discharge as well as the characteristic of the falling limb.
* The size of the drainage basin will affect the shape of a storm hydrograph as
smaller drainage basins will mean that overland flow will more quickly reach
the river and so create a steeper rising limb and a shorter lag time.
* The shape of drainage basin will affect the shape of a storm hydrograph as
more rounded drainage basins will mean that overland flow will more
quickly reach the river and so create a steeper rising limb and a shorter lag
time.
* The drainage density of the drainage basin will affect the shape of a storm
hydrograph as drainage basins with a high drainage density will mean that
overland flow will more quickly reach the river and so create a steeper rising
limb and a shorter lag time.
* The rock type of the drainage basin will affect the shape of a storm
hydrograph as drainage basins with impermeable rocks such as granite will
mean that overland flow will more quickly reach the river and so create a
steeper rising limb and a shorter lag time.
* The soil type of the drainage basin will affect the shape of a storm
hydrograph as drainage basins with soils with a low infiltration rate such as
clay soils will mean that overland flow will more quickly reach the river and
so create a steeper rising limb and a shorter lag time.
* The topography of the drainage basin will affect the shape of a storm
hydrograph as drainage basins with steep slopes will mean that overland
flow will more quickly reach the river and so create a steeper rising limb and
a shorter lag time.
* The vegetation type and amount of the drainage basin will affect the shape
of a storm hydrograph as drainage basins with sparse vegetation will mean
that overland flow will more quickly reach the river and so create a steeper
rising limb and a shorter lag time.
* The levels of antecedent soil moisture will affect the shape of the storm
hydrograph as saturated soils will mean that overland flow will more quickly
reach the river and so create a steeper rising limb and a shorter lag time.
