1.1.7 - the role of aeolian, fluvial, biotic proccesses in the formation of of coastal systems Flashcards
where do sand dunes occur?
at the highest tide level, and further extend inland
what conditions do sand dunes need to occur?
- abundance of sand
- low beach gradient
- strong onshore wind
- area inland
- vegetation
how does the sand get transported by the wind?
saltation
what does a low sediment supply result in for a sand dune?
the foredune is vulnerable to aeolian erosion, and blowouts and often a parabolic sand dune
what is a parabolic sand dune?
a sand dune that got blowout, where the tip is solidified by vegetation and creates a u-shape
why are pioneer plant species important to sand dunes?
the can survive many different conditions, by taking root in the sand dune and stabilising it by friction in its roots
what is an example of pioneer species?
sea couch grass
what is the lifecycle of a sand dune?
embryo dunes
foredunes
yellow dunes
dune slack
grey dunes
woodland
how does an embryo dune occur?
- sand collects by driftwood and grass/pioneer species begin to grow up to a few metres
- these are smaller and have a shallower gradient
what are some pioneer species?
sand couch, lyme grass
what occurs at a foredune?
these are larger dunes, stabilised by marram grass as predominant vegetation
what occus at a yellow dune?
where patchy marram grass with leaves which are useful to reduce wind
what occurs at a dune slack?
here, sandy soil is developed, supporting taller woody species or plants like brambles
- slack gets even worse with wind erosion getting faster down lee slope - erodes down to water table and sometimes makes lagoons
what occurs at a grey dune?
these are fixed sand dunes, covered in vegetation, moss/lichen begin to colonise which gives it grey colour
what occurs at the woodland area of sand dunes?
colonised by trees, tolerant of all beach conditions
what is the purpose of a sand dunes water table?
gives vegetation to the water to grow
what is a lee slope and a stoss side?
lee side - inland
stoss side - towards sea
define a blowout?
where the vegetation has been removed (animals) , this allows the sand to get removed by the wind due to the lack of friction and stabilisation
where does sediment come from, found in estuaries?
rivers/fluvial
cliff erosion
sediment sinks
whats another term of longshore drift?
littoral drift
what is a tidal flat?
largely depositional areas around the edges of estuaries, containing sand & mud, less energy
where is the coarser sediment deposited?
in the more energetic estuarine mouth
how are salt marshes catagorised from fluvial processes in estuarine environments?
macro-scale - horizontal platform that slopes seaward
micro-scale - channels/rills around rocks
why are salt marshes horizontal platforms?
the sediment is brought onto the marsh surface and trapped by vegetation - SEDIMENT ACCREATION
