landforms Flashcards
what is a beach
accumulation of sediment, they are important temporary stores within sediment cells
where do beaches form
between high and low water mark
what are beaches formed of
material from offshore sand bars, longshore drift, wind blown sand and mass movement
what 4 types of beach are there
shingle vs sand
swash vs drift
what is the difference between shingle vs sand beaches
shingle : high energy, steeper, 10-20 degrees
sand : low energy, sloping, 5 degrees
what is the difference between swash align and drift align beaches
swash : waves approach parallel, swash and backwash same angle
drift : waves approach at an angle, retreat perpendicular, creates a zig zag motion
what is a discordant coastline
alternating bands of rock at a right angle
what is a concordant coast line
alternating bands of rock parallel to the coastline
what is the process of caves, arches, stacks and stumps forming
- wave action is concentrated on headlands (wave refraction) through erional processes cracks/faults are exploited
- over time this creates a cave
- where cave faces oncoming waves, force is applied directly to rear of cave forming a blow hole
- over time further erosion breaks through to create an arch
- weathering on top of the arch causes it to collapse making a stack
- further erosion and weathering creates a stump
what factors are involved in the formation of caves, arches, stacks and stumps
- high energy coastline, destructive waves
- erosional processes
- wave refraction
- amount/severity of cracks and faults
example of cave, arch, stack and stump
Old Harry in Dorset
how are wave cut platforms formed
- wave action concentrated at high tide line
- over time creates a wave cut notch
- weathering on top + further erosion of the hitch causes cliff to become unstable and collapse
- leaves behind a wave cut platform
- this process repeats
- they are fairly smooth and flat due to abrasion
why do wave cut platforms rarely extend further than 500m
longer the platform the further the waves have to travel, waves will break earlier and won’t reach the cliff, erosion of the cliffs won’t occur
what are the factors involved in the formation of wave cut platforms
- erosion
- weathering
- tides
- geology
what are cusps
crescent shaped indents in the shape of the coastline
where are cusps formed
sand and shingle beaches, heavier sediment is dropped at the horns
how are cusps formed
waves hit horns and drop heavier sediment, curved sides channel incoming swash into the centre of the cusp which creates stronger backwash flowing out of the centre, deepening it
what is a berm
raised, wide flat area at the back of a beach
what are ridges, runnels and ripples
ridges are raised lines on the beach
runnels are depressions that form behind ridges
ripples are smaller versions of ridges and runnels
why do ridges, runnels and ripples form
due to tide action moving back and forth
what are spits
long narrow ridges of deposited sediment that form where the coastline changes direction, typically over estuaries
how do spits form
longshore drift
where is the coarser sediment
proximal end
where is the smaller lighter sediment
distal end
what is a simple spit
has one recurved end, no minor spits
what is an example of a simple spit
spurn head
what is a complex spit
have multiple recurves, minor spits, show previous position of the spit
what is an example of a complex spit
hurst point
what factors effect the formation of a spit
- low energy environment + constructive wavesfor deposition
- prevailing wind creating drift align coast
- geology
- shape of coast has to change
what is a barrier beach
accumulation of sediment that connects two headlands
how do barrier beaches form
either when a spit extends across the bay or when glaciers melted and deposited sediment in the last ice age
what is a tombolo
mound or ridge of sediment that connects the main land to and island
how does a tombolo form
from wave refraction
what is an example of a barrier beach
Slapton Ley
what is an example of a tombolo
Angel Road, Japan
what is a barrier island
offshore deposit of sediment
where do barrier islands form
Usually in areas of low tidal ranges and gently sloping offshore coastlines
how are barrier islands formed
when glaciers from the last ice age 18,000 years ago and deposited their sediment
what may happen on barrier islands
may become vegetated
how do sand dunes form
- sand is initially trapped by obstacles (storm berm where drift wood is)
- obstacles grow, slows wind further leading to more deposition
- pioneer species grow such as marram grass
- these stabilise the dunes
- die and decompose providing nutrients for other species
- climatic climax when mature trees grow such as oak
what is the order of dunes
embryo, yellow, grey and mature
how tall is an embryo dune
1m
how tall is a yellow dune
5m
how tall is a grey dune
8-10m
what may form between dunes
dune slacks, where the water table is at surface, aquatic ecosystems may form
where do mudflats/salt marshes form
sheltered areas/ low energy environments such as behind an estuary
how do mudflats/salt marshes form
- sediment builds up as velocity is low
- flocculation = slow flowing water meets saline sea, clay particles join together, sink to bed of estuary
- salt tolerant plants grow such as eelgrass
- pioneer species grow such as cordgrass (halophyte)
deposition continues, plants continue to grow + die - surface of marsh raises, submerged for shorter periods of time
- mudflat becomes a salt mash
- more comped flowering species like sea lavender establish
- deposition continues
- climax vegetation when marsh rises above level of spring high tide
what is an offshore bar
submerged or partly exposed ridges of sand or coarse sediment created by waves and currents offshore of the coast
what do offshore bars act as
sediment sink
absorb wave energy, less erosion
