Coasts AS Geography (WJEC)

coasts are

dynamic open systems

what is the sediment budget

sediment available, stored, sourced and transferred

fluvial sediment comes from

rivers

aeolian transfer is via

wind

if there is a net loss of sediment there is

more erosion

sediment cells / littoral cells are

units of coastal management

how many major sediment cells in england and wales

11

major cell :

a length of coastline and its associated nearshore area within which the movement of course sediments is largely self-contained

steady state equilibrium

energy and morphological response aren’t far from the average

metastable equilibrium

switching between two or more states of equilibrium often caused by a trigger event

dynamic equilibrium

a change in equilibrium gradually

positive feedback

amplifies the original change

negative feedback

diminishes the effect of change

semi diurnal tide

2 high 2 low every 24 hours

diurnal tide

1 high 1 low every 24 hours

where has diurnal tides

antarctica

spring tide

twice a month above average

neap tide

twice a month below average

spring tide arrangement

sun and moon aligned

neap tide arrangement

sun and moon at right angles respective to earth

amphidromic points

little to no difference in tidal height

tidal range

height difference between high and low tides

spring tides have

high tidal range

neap tides have a

low tidal range

micro tidal

less than 2m

macro tidal

bigger than 6m

where is micro tidal

east coast of australia

where is macro tidal

north america

what occurs during rise and fall of the tide

wetting and drying of the substrata and salt weathering

sand dunes are often found in

macro tidal environments

flood tide

incoming tide, raises sea levels

ebb tide

the outgoing tide, lowers sea levels

shore-normal currents

approach the shore parallel

rip currents

travel away from the beach

longshore currents

responsible for longshore drift

how to calculate steepness of wave

height / length

what is the wave base

no movement at the depth of half a wavelength

wave period of sea waves

1-20 seconds

constructive waves

strong swash, long wavelength and period, low energy, summer

destructive waves

strong backwash, short wavelength and period, high energy, winter

waves depend on

wind velocity and duration, fetch, orientation of coast to waves

clapotis effect

waves reflected from cliffs don’t break and are reflective so a standing wave is created

high energy coastlines e.g.

great coast road, victoria, australia

low energy coastlines e.g.

netherlands

depositional landforms occur at

low energy coastlines

igneous rocks

cooled lava / melted rock

example of igneous rock

granite

metamorphic rocks

formed by heat and pressure

example of metamorphic rock

gneiss

sedimentary rocks are made from

layers of sand silt and dead biotic matter

examples of sedimentary rock

limestone and sandstone

which types of rock are MORE resistant to erosion

igneous and metamorphic

sumatra’s rates of erosion and why

30m a year from the krakatoa ash

oxidation

breaking down iron rich rocks with oxygen and water

hydrolysis

acidic water breaks down rocks into clay and soluble salts

carbonation

chemical decomposition of limestones

carbonation is also called

saltwater corrosion

if a rock is more permeable it is

more resistant to subaerial processes

joints

often vertical fractures in rock

faults

major fractures

bedding planes

horizontal lines separating layers of rock

example of geos

island of skomer pembrokeshire

folds

stretched or compressed rock

example of folds

saundersfoot tenby

examples of physical/mechanical weathering

saltwater crystal growth, ftw, wetting and drying

examples of chemical weathering

solution, hydration, hydrolysis, oxidation, chelation

acronym for examples of chemical weathering

sandra’s hefty horse offends cats

what is hydration

minerals absorb water which weakens the structure

what is chelation

organic acids from plant roots bind to metal ions

example of rockfalls

svalbard

example of rockslides

tenby

example of rock toppling

giants causeway northern ireland

what is creep

downslope movement of regolith

what is regolith

loose material above the bedrock including soil

what is solifluction

the slow downslope movement of regolith, saturated by the melting of the active layer above the permafrost

hard rocks produce

steep cliffs

what is managed realignment

creating new saltmarshes by removing coastal defences or moving further inland

limestone retreats at

1 cm a year

clay can retreat as much as

100 cm a year

disconcordant coast

made up of different types of rock at different places

example of blowholes

spouting horn kauai hawaii

geos are formed when

a blowhole roof collapses

stoke’s law

sediment deposited is directly proportional to the mass of the sediment

flocculation

clay particles aggregate together to form flocs

storm beach

largest boulders thrown above high-water mark

swash aligned beaches

waves parallel, no longshore drift

drift aligned beaches

waves oblique angle, longshore drift

zeta formed beaches

at an oblique angle to the dominant waves, longshore drift, headlands at each end

bar

spit that joins two headlands

example of a bar

frisian islands

tombolo

when longshore drift joins two islands

example of tombolo

tombolo di orbetello tuscany

cuspate foreland

triangular projections pointing out to sea

example of cuspate foreland

dungeness foreland in kent

conditions for dunes to develop

sand supply, low gradient, macro tidal, onshore winds, inland space, vegetation

parabolic dunes

collapsed centre

order of dunes

embryo, fore, yellow, grey

which dunes are fixed

grey

pioneer plant species characteristics

can survive water scarcity, mobile land, high salt conc, strong winds and low nutrients

examples of pioneer plants

sand twitch, sea couch grass, marram grass and roots