2B.3 Rates of Coastal Recession Flashcards
lithology, rock strata and vegetation
name the three rock types
igneous
metamorphic
sedimentary
igneous rock
e.g. granite, basalt, dolerite
-interlocking crystals cause erosion rate to be very slow
-granite has few joints, limiting weaknesses available for erosion to exploit
metamorphic rock
e.g. slate, marble
-crystalline rocks are resistant to erosion
-some have a feature with the same direction crystals, causing weaknesses
-folded and heavily fractured for erosion to exploit rocks, erosion is slow
sedimentary rock
e.g. sandstone, shale, chalk and limestone
-erodes faster than others
-younger rocks are weaker
-bedding planes and fractures create vulnerability to erosion
what is the weakest coastal material
unconsolidated sediment
what factor of rocks influences cliff profiles
PERMEABILITY
permeable rocks
allow water to flow through e.g. sandstone and limestone
impermeable rocks
do not allow groundwater flow e.g. clays, mudstones
how can impermeable rocks become weak?
groundwater flow weakens rocks as it removes cement that binds sediment together in the rock
-also it creates a high pore water pressure, making the rock heavy, affecting its stability
describe a dalmation coastline
-concordant coastline
formed due to a rise in seal level, the tops of ridges can be seen above sea level which creates a series of offshore, long, thin islands
describe a haff coastline
-concordant coastline
it is enclosed by low lying sandy spits or dunes which are aligned parallel to the coast
-longshore drift occurs
describe a fjord
-discordant coastline
formed when deep glacial troughs flood by rising sea levels, cutting deep valleys perpendicular to the coastline, they are very deep
-found in Norway and west Iceland
describe a ria
-discordant coastline
these are drowned river valleys which are sheltered winding inlets formed by rising sea level, they are narrow and form natural harbours at the coast
e.g. Falmouth is the deepest natural harbour in the UK
what vegetation is found on a haff coastline?
marram grass
marram grass adaptations and features
it is a common type of grass that has a waxy, hard coating
-durable to winds and storms
-rounded tube shape to retain moisture
-deep roots to access more water
-wide roots for stability and reaching minerals and water
-halophyte plant with salt spray
stability
the protection of coastlines by vegetation such as sand dunes and salt marshes
succession
the changing nature of a plant community over time as an area is colonised
psammorsene
the succession of plants that develop on a sand dune complex
flocculation
the process by which river’s load of clay and silts carried in suspension is deposited more easily as it meets with sea water (salt)
halosene
the succession of plants that develop in a salt marsh
how do sand dunes play a role in the coast
it protects the coastal landscape from erosion by stablising plants
-they are important buffer zones between the sea and land, they take the impact of storms, reducing the impact on the land
describe how vegetation stabilises coastal deposition features
- plant roots bind sediment together, reducing erosion
- when submerged, plants provide a protective layer so the surface of sediment is not directly exposed to moving water (salt marshes)
- plants protect sediment form wind erosion, reducing speed at the surface with friction against the vegetation
how are halophytes salt tolerant?
they store water in special tissue with air spaces
-some excrete salt through glands or by dropping yellow leaves where salt has been accumulated
-they retain water- succulents
how are xerophytes dry condition tolerant?
they have thick cuticles to stop uncontrolled evaporation, with a small leaf surface area too
-low stomata density
-sunken stomata maintains humid air
-stomatal hairs
-rolled leaves
-extensive roots maximise water uptake
when is a climax community reached?
when the vegetation is in a state of equilibrium with the environment
name 3 wind processes
suspension, impact creep, saltation
describe suspension
moves fine grains of sand in the water (1%)
describe impact creep
moves the heaviest grains in water (4%)
describe saltation
moves intermediate sand grains (95%)
-in WATER AND ON BEACHES
name the 5 stages of sand dune formation
-embryo/ fore dunes
-yellow dunes
-grey dunes
-dune slacks
-woodland
describe the embryo and fore dune stage
mobile dunes
-plants have waxy leaves to retain moisture and withstand strong winds, high salt tolerance
-offshore winds cause sand to build up slowly, it accumulates above the high tide line, causing a colonisation of grasses
-dead marram grass adds organic matter and nutrients to the soil
describe the yellow dune stage
mobile dunes
-vegetation develops on the upper and back dune surfaces, stabilising the system
-surface is being blown away and replenished with new sand
-once stable conditions occur, mosses and cover patches
describe the grey dune stage
fixed dune
-more soil is trapped with nutrients and moisture
-high diversity of species
-more plants colonise with more organic matter
-dunes may be trampled on or grazed on, organic layer forms on the soil surface
describe the dune slack stage
fixed dune
-moisture loving plants colonise here
-there is a damp environment, with a high water table in winter
-plants receive nutrients leached from the surrounding dunes
-is now rich will local and national rare species
describe the woodland stage
sandy soils have developed that can support scrub heaths of willow and other trees
-acidic soils and high organic matter content
-cattle or grazing pressures can prevent woodland development
-vegetation is dominated by plants that are adapted to grasslands and heathlands.
aeolian processes
wind processes
what type of landforms are sand dunes and salt marshes
depositional landforms
salt marshes
areas of flat, silty sediment from rivers that accumulate around estuaries or lagoons, affected by the sea
fluvial
river processes
characteristics of salt marshes
-sheltered environment
-salt and freshwater meet
-no strong currents or tides, so deposition and accumulation occurs
describe the flocculation process
as clay and silt are carried in suspension, they are deposited easily as they meet with salt in sea water
-clay particles are small and negatively charged (remain suspended)
-in the estuary, river water mixes with sea water, so the charges on clay particles are neutralised, they flocculate (stick together) and settle out (sedimentation)
-building up a muddy shore in an estuary
why must wave energy be low in salt marshes?
low energy must be present for a salt marsh to develop, so sea water can deposit the smaller clay particles and so they cling to eachother in flocculation
e.g. behind spits, in bays or on the top of long flat beaches
describe the development of salt marshes
- first colonised by algae which helps to stabilise the surface of mud and reduce erosional processes by waves and tides
- the colonisation of glassworts stabilises the mud, adding organic matter so vegetation can grow
- this interrupts the flow of water, encouraging more deposition
name 5 stages of salt marsh succession
algal stage
pioneer stage
establishment stage
stabilisation
climax vegetation
when are salt marshes covered and exposed?
they are covered at high tide and exposed at low tide
