coasts Flashcards
what are the characteristics of rocky coasts
resistant geology
(withstands erosive forces of sea, rain and wind), often in a high-energy environment
erosion > deposition
what are the characteristics of costal plain landscapes
deposition > erosion
found near areas of low relief and result from supply of sediment from different terrestrial and offshore sources, often in a low-energy environment.
deposition and transportation
what is responsible for concordant and discordant coastlines
Geological structure is responsible for the formation of
concordant and discordant coasts.
what is geological structure
Geological structure (jointing, dip, faulting, folding) is an important influence on coastal morphology and erosion rates, and also on the formation of cliff profiles
Geological structure influences coastal morphology: Dalmatian and Haff type concordant coasts and headlands and bays on discordant coasts.
dipping comes under geological structure, what are the 4 types of dipping
-horizontal dipping= more easily eroded
-seaward dipping (low angle)= may produce overhanging rock that is vulnerable to rock falls
-seaward dipping (high angle)= vulnerable to rock slides
-landward dip= stable cliff, reduced rock falls
what does rates of costal recession depend greatly on
-bedrock lithology (igneous, sedimentary, metamorphic) and unconsolidated material (boulder clay) geology are important in understanding rates of coastal recession
- alternating strata in cliffs (permeable/impermeable, resistant/less resistant) produces complex cliff profiles and influences recession rates. (differential erosion)
-Vegetation is important in stabilising sandy coastlines through dune successional development and salt marsh successional development in estuarine areas.
-geological structure
what marine erosion processes contribute to distinctive costal landscapes
- wave type (constructive and destructive)
-erosional processes (HA, Corrosion, abrasion, attrition)
apart from marine erosion, what other processes affect distinctive costal landforms
-transportation and deposition
-subaerial processes
-bedrock lithology and geology
-plant succession can stabilise coastlines
what distinctive costal landforms does marine erosion create
wave cut notches, wave cut platforms, cliffs, the cave-arch-stackstump sequence
what is sediment transportation influences by
s influenced by the angle of wave attack, the process of longshore drift, tides and currents.
what distinctive costal landforms does deposition and transportation create
(beaches, recurved and double spits,
offshore bars, barrier beaches and bars, tombolos and cuspate forelands), which can be stabilised by plant succession.
what do sediment cells explain
equilibrium and positive and negative feedback
what is contempory sea level change caused by
-global warming
-tectonics
sea level change has produced emergent coastlines, what are they
-raised beaches (a old beach now above tide level)
-fossil cliff (a steep slope found behind a raised beach exhibiting past evidence of marine erosion)
sea level change has produced submergent coastlines, what are they
-dalmation coastline
-ria
-fjard
-fjord
define eustatic
(ice formation/melting,
thermal changes)
define isostatic
(post glacial adjustment,
subsidence, accretion and tectonics
land rises and falls relative to the sea
what is rapid costal recession caused by
caused by physical factors
(geological and marine)**WHAT but can be influenced by human actions (dredging or coastal management) ( the Nile Delta
Rates of recession are not constant and are influenced by different factors both short- and longer term, what are these
(wind direction/fetch, tides, seasons, weather systems and occurrence of storms
what local factors increase flood risk
-low lying land
-degree of subsidence (water abstraction can lead to isostatic sinking seen in bangladesh and weight of the built environment can compress sediment leading to subsidence)
-levels of vegetation
a global factor is sea level rise
what was the total cost of damage due to cyclone sidr
total damage estimated as $1.7 billion
what did the IPCC identify in terms of future climate change
-that depressions are likely to become more common leading to greater storm surges
-medium confidence of stronger winds
what is sustainable costal management
- relocation
-monitoring costal change
-educating communities
-adapting to sea level rise
-managing flood risk
how much does a sea wall cost per metre
£3000-£10,000 per metre
how mcuh does beach nourishment cost per KM
£20 million per KM
whats CBA
Cost benefit analysis
whats EIA
environmental impact assessment
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
what is mass movement impacted by
-the angle of the slope or the cliff
-the rock type and its structure
-the vegetation cover
-how wet the ground is
mass movement flows:
whats soil creep
-slow downhill movement of individual soil particles
mass movement flows:
whats solifluction
-occurs where the ground is frozen. The thawed surface layer flows over the frozen subsoil and rock
mass movement flows:
whats earthflows / mudflows
an increase in the amount of water can reduce friction- causing earth and mud to flow over underlying bedrock
whats the difference between a slide and a flow
in a slide, the material remains intact, in a flow the material becomes jumbled up
mass movement slides:
what are rock falls
occur when jointed and steep rockfaces are exposed to mechanical weathering.
-fallen material forms tallus/scree
mass movement slides:
what are block falls
a large block of rock falls away from the cliff as a single piece
mass movement slides:
what are rock/ debris slides
an increase in the amount of water can reduce friction causing sliding. Slabs of rock/ blocks can slide over underlying rocks along a slide or slip plane
what are slumps
occur on moderate steep slopes in saturated conditions
rotational movement occurs
-slumping causes rotational scars
-repeated slumping creates a terraced cliff profile
