EQ3 Flashcards
what are the three reasons why sea levels are rising?
Global warming- ice caps and glaciers are melting
thermal expansion- as seas heats up it expands and takes upp more space
tectonics
- thermal expansion (as the sea heats up it expands and takes up more space)
what is eustatic change
when the sea level itself rises and falls. The change is global. In cold glacial periods precipitation falls as snow and forms ice sheets which store the water. At the end of a glacial periods as climate warms, the ice melts and sea levels rise.
whats isostatic change
when the land rises or falls relative to the sea. The change is local. In cold glacial periods the enormous weight of the ice sheets makes the land sink (isostatic subsidence). At the end of the glacial period as the climate warms, the ice melts and the land rises as the weight of the ice sheets reduce (isostatic recovery/ rebound)
what category does thermal expansion come under
eustatic
what category does ice caps and glaciers melting come under
eustatic
what category does terrestrial water storage, extraction of groundwater, building of reservoirs, changes in runoff, and seepage into aquifers come under
eustatic
what category does subsidence in river delta region, land movements and tectonic displacements come under
isostatic
what category does surface and deep ocean circulation changes, storm surges come under
eustatic
Kiribati case study- what is next and why are sea levels rising
- only 1 meter above sea level
- made up of 33 islands
- sea levels are rising due to global warming
- rising sea levels are contaminating groundwater
- people will have to move to Fiji
- population will become environmental refugees
what are submergent coastlines a result of?
sea level rise or isostatic sinking
what are the 4 submergent coastlines?
a ria, a fjord, a fjard, dalmation coats
submergent coastline: whats a ria
Narrow wonding inlet which is deepest at the mouth
- - associated with a rise in sea level
- occur when a valley is flooded
- they are sheltered winding inlets with irregular shorelines
- common in south west England
submergent coastline: whats a fjord
Flooded glaciated u shaped valley with very deep water and steep sides
- - formed when deep glacial troughs are flooded by a rise in sea level.
- the shallower entrance marks where the glacier left the valley
- can be seen in Norway
submergent coastline: whats a fjard
a flooded inlet with low rocky banks on either side
- formed by post glacial drowning of glaciated low and rocky terrain .
- can be seen in the gulf of finland
submergent coastline: whats a dalmatian coast
- rivers flow parallel to the coast
ridges run paralle to the coast
- can be seen in croatia
what are emergent coastlines caused by
a result of isostatic rebound
rise in land
whats an emergent coastline (example)
raised beaches/ fossil cliffs
emergent coastline: how does a raised beach/ fossil cliffs/relic cliffs occur, what is it
as the land rose as a result of isostatic recovery, former shoreline platforms and their beaches were raised above the present sea level.
often the remains of relic cliffs (eroded cliff lines) can be found behind the raised beach, with wave cut notches and caves as evidence of past erosion.
- can be seen on the west coast of scotland
why does past tectonic activity have a direct impact on some coasts across the world, as well as sea levels?
due to the fact that they cause:
they may have a direct effect on the shape of a coast and coastla processes
- uplift of mountain ranges at costal land at destructive and collision plate margins
- local tilting of land, for example, some ancient Mediterranean ports have been submerged and others have been stranded above the current sea level
risk o tsunamis
what are physical factors contributing to costal recession
- weathering
- mass movement
- geology
- marine processes
- large destructive waves (up)
- small constructive waves (down)
- resistant rock
- constant weathering
- large scale mass movement
- weakly consolidated rock
what are human factors contributing to costal recession
- offshore dredging
- costal development
- costal defences/ costal management
- make case study Holderness mind map
located in east yorkshire
-consists of lsd, geogoly, fetch and subariel
geology=unconsilated material-easily eroded- 2m a year
fetch- fetch isnt large norht sea- north sea is relatively depp doesnt experience and friction- hits land at a greater force- more erosion occures.
subariel processes
lsd-casues tgs- groynes paced at hornsea- starved mappleton- causing unequal distribution of sedimemt along the coast
social by 2100 200 homes will be lost
loss of recertional space and amenity value
econ
local tourism loses money, 1.2mil spent on repairs
env
loss of coatsl habists
up to 4m los in some spaces
what is dredging
the removal of material from the seabed- used to make ports, beach nourishment
what are the negatives of dredging
- difficult for kids to do activities (e.g snorkelling)
- removing seafloor species and damaging coral
- increased swell as result of deepening the bay- resulting in erosion and need for costal defences
- sediments converting marine communities
what are the positives of dredging
- port capacity increased- improved trade and navigation
- may offset isostatic sinking
- extra sediment and deposition may offset sea level rise (naturally or beach nourishment)
case study- the nile delta and sea level rise and human activity.
- the delta is experiencing retreat, significant erosion on half of it.
- there is salt intrusion due to sea level rise
- 2 million hectares of fertile land could be lost
- at least 6 million people displaced
- there is an integrated costal zone management ICZM
- building of aswan dam reduced the sediment supply
- coastal flooding will be more frequent
what are the main 5 factors affecting costal recession:
wind direction, weather systems, seasons ,tides, storm activities
costal recession: wind direction
- the dominant wind produces the largest wave, most erosion occurs here, less erosion when winds are from other directions
- links to fetch and how much the wavy can build up
- a longer fetch means a more powerful wave
costal recession: tides
- there are two high tides and two low tides a day.
- high tides=spring tides (when sun and moon are aligned so gravitational pull=strongest)
- low tides= neap tides(when sun and moon are at right angles to each other)
- tides determine where the waves will reach the shore
- erosion at max when high tide is with destructive wave
costal recession: weather systems
high pressure- air sinking- leads to dry conditions- brings about calmer conditions and smaller waves
low pressure- rising air- leads to wet weather- strong winds rotating in anticlockwise direction- larger waves
wind wants to go from high to low pressure zones- global warming has added more heat thus intensifying low pressure systems
costal recession: storm activity
linked to a low pressure weather system, notably tropical cyclones and depressions. when air pressure is low over the sea, water is able to rise upwards, forming a dome of sea water under the depression. the lower the air pressure the higher the dome will be . the dome of water can then surge when the low pressure system moves near a coast. as tropical cyclones/ depressions are associated with strong winds, they create large storm waves the will appear on top of the dome. this adds height to sea levels and increases the risk of costal flooding, can join with high tide {all storms are low pressure systems}
costal recession: seasons
winter waves= more destructive than summer waves.
winter waves- depressions are greatest - greater variety in difference in high and low pressure areas- greater wind speeds- low air pressure and faster winds- winter= season for hurricanes and storms (low pressure)- more erosion
how do mangroves reduce threat of costal flood risk
- reduce height of waves by 40%
- stabilises and traps sediment by keeping the land higher
explain 3 physical reasons why some locations are at risk of flooding
- subsidence
- sea level rise
- removal of vegetation
what is the amenity value
its the value in cultural , human wellbeing and economic terms of an attractive environment that people enjoy using
how does the level of development impact the consequences of costal flooding: Australia a developed country (soc, econ, env)
ECON: -tourism affected -$67 billion road and rail at risk SOC: -hospitals and health services at risk -close to 250,000 homes at risk ENV: -mangrove forests at risk -great barrier reef at risk
how does the level of development impact the consequences of costal flooding: Philippines: developing/emerging country (soc, econ, env)
ECON: -losses of $6.5 bil a year -costal defences= expensive SOC: -around 2.3 mil affected -high level of unemployment ENV: -corals and sea grass have been damaged by pollution
5 soft engineering techniques
- beach nourishment
- cliff drainage
- cliff regrading
- managed retreat
- dune stabilisation
6 hard engineering techniques
- groynes
- sea walls
- rip rap
- revetments
- offshore breakwaters
- gabions
what does sustainable costal management mean
it means managing current and predicted future risks to the wider costal zone in terms of peoples economic livelihood, social wellbeing and local culture and environmental impacts
what are stakeholders
an individual or group of people who have an interest in the outcome of decisions made to change areas.
what are winners
people who gain from a decision , either economically, environmentally or socially
what are losers
people who are likely to lose property, their job, be forced to move, or see the coastline concreted over and view this as an environmental negative
what are the 4 choices that can be made by the ICZM (integrated costal zone management)
- advance the line
- hold the line
- managed retreat
- no active intervention
