coasts Flashcards
what does the littoral zone consist of?
backshore,foreshore, nearshore and offshore
describe a rocky coast and a coastal plain
result from resistamt geology
-high relief
-withstand erosive forces
-often in high enegry env
result from a supply of sediment
-different terrestrial and offshore sources
-low relief
-low enegry env
sandy and eastury coast
igneous and examples
created by volcanic activity when magma or lava cools, forming crystals that are normally hard- granite and basalt
sedimentary and examples
formed by small particles that ahve been eroded, transported and deposited in layers (sandstone) or from remains of plants and animals (limestone and chalk)
metamorphic and examples
form from other rocks changing by extreme heat and pressure usually form from layers/bands of crystals and very hard. Shale can be compressed into SLATE and limestone can be transformed into MARBLE
what coastline does sedimentary rock have?
and landforms
- flat low lying relief
- low energy env
- beaches, spits and salt marshes, lagoons
low lying sandy beaches
what coastline does igneous rock have?
and landforms
rocky outcrops, resistant to ersion, high energy env
stack stump, wave cut platform
what is costal morphology
the shape and form of costal landscape and their feature.s
what is lithology
type of rock, sedimentary, metamprphic uncolidates, igenous…
what is geology
concordant dicordant coasts
joiting, dipping, faulting, folding ( e.g. these can form caves)
what is strata
layers of rock
what are bedding planes
(horizontal cracks) these are natural breaks in the strata,, caused by gaps during periods of rock formation
what are joints
(vertical cracks) these are features caused by either contraction as sediments dry out or by earth movements during uplift.
what are folds
formed by pressure during tectonic activity, which makes rocks buckle and crumple
what are faults
Faults are major fractures in rock created by tectonic forces
what’s a dip
this refers to the angle at which the strata lie (horizontally, vertically, dipping towards the sea or dipping inland)
what is the relief ( or height or slope of the land) affected by
geology and lithology
what are the 3 things that lithology includes
- rock type metamorphic sedimentary igneous
- how porous the rock is (permeability) linked to grain size and rock structure (crystal)
- vegetation
erosion rate of igneous rock?
1mm per year
erosion rate of sedimentary rock?
2.5cm per year
erosion rate of unconsolidated material?
1m per year
what’s a discordant coastline eg
where the geology alternates between more resistant bands of rock with less resistant bands, cut at right angles to the coast (perpendicular)
east facing dorset=isle of purbeck
headlands and bays
what’s a concordant coastline eg
where bands of more resistant and less resistant rock run parallel to the coast.
south facing dorset
a real life example of a concordant coast?
and explain formation process
litholgy, dip,small features, creates sea cave.
lulworth crumple is created by the collisiion of the african and eaurasion plates. pressure and cooling forms cracks in rocks. joints aer made as sedimentary rock is formed from pressure.micro geology forms points of weakness
dip- if rock layer dips towards the sea- blocks of rock to slide under the influence of gravity(Mass M) if dip landwards- weathering and erosion may attachk bedding planes- creating irregular profile.
cliffs may create protruisions(sticking out) and indentations, blowholes, geos
weka point(joint), weathered or eroded creating a sea cave.
describe Dalmation coastlines
-concordant coastline
submerged landform
-valleys and ridges run parallel to each other
-past valleys have flooded and ridges are left over
produce long islands and inlets.
describe haff coastlines
- concordant
- long spits and lagoons aligned parallel to the coast
what are the two types of vegetation that protect the coast
salt marshes and sand dunes
what are salt marshes
+ detailed explaination
areas of flat, silty sediments that accumulate around estuaries or lagoons
- tidal conditions bring seawater and sediment in and out,
- rivers bring fine mud deposit at side of estruy
flocculation occurs- colonised by algae
3.pioneer plants survive with brackish water
more sediment is trapped builfing uo salt marsh
where do salt marshes develop
- in sheltered areas where deposition occurs
- low enegry env
- where there are no strong tides or currents
what are pioneer plants referred to as
the first colonizing plants
what do pioneer species do
modify the environment by binding sand or soil with their roots and adding nutrients when they die or decay
what helps retain moisture for sand dunes, mud dunes and salt marshes.
creeping plants or those with leaf cover
what helps slow down tidal flow and trap more mud and salt
halophytes (salt tolerant species)
-eg cordgrass
what are the first dunes to form called?
embryo dunes
how does vegetation help protect the coast
it modifies the environment by binding the sand and soil with its roots. More vegetation means less erosion as sand and soil becomes more stabilized and less vulnerable
constructive waves lead to ______
deposition
destructive wavs lead to ______
erosion
what is the crest
the peak of the wave
what’s the wave trough
the lowest point of the wave
what’s the wave height
the distance between the crest and wave trough
what’s the fetch
the distance of water that a wave can build up
state the wave form, wave break and frequency of constructive waves
low surging wavs with a long wavelength.
string swash, weak back swash
beach gain with 6-9 per min
state the wave form, wave break and frequency of destructive waves
high plunging waves short wavelength
weak swash strong back swash
beach loss
11-14 per min
what dos summer do to a beach profile?
steeper profile due to common constructive waves-
lowland coast, coastla plain.
constructive waves have a lower frequency than destructive waves so waves energy dissipates and deposits over a wide are
what does the winter do to a beach profile
destructive waves are frequent so berms~ are eroded
shallower profile as berms eroded
strong back swash transports sediment offshore creating offshore bars
what two moons have tides at max height and highest tidal range
spring tide (full moon) spring tide (new moon)
what two moons has the smallest tidal range and lowest tides
neap tide (first quarter moon) neap tide (last quarter moon)
what is abrasion
- also known as corrasion
- waves pick up sand and pebbles and when waves break, transported material is hurled at the cliff, chipping away the rock
- rocks/sediment=thrown
what is hydraulic action
when a wave advances, air can be trapped/compressed into the joints. when the wave retreats, trapped air expands.
- this continuous process weakens joints and cracks causing rock to break off
- can erode by hammer like pumping effects
what is solution
the chemical process that breaks down rocks by dissolving them in water
what’s attrition
the gradual wearing away of rock particles by impact and abrasion, as the pieces of rocks are moved by waves, tides and currents.
this gradually reduces particles size making stones rounder and smaller.
name some erosional landforms
headlands and bays, stacks, stumps, shoreline platforms/wave cut platforms and wave cut notches
how is a wave cut platform/shoreline platform created
- destructive waves bash into the base of the cliff
- eroded by ha, abrasion, corrosion
- continues making wave cut notch bigger and bigger then collapses
- cliff retreats leaving a wave cut platform/shoreline platform
how is a stump formed (7 steps)
1- large crack opened by ha
2-the crack grows into a cave by ha and abrasion
3-the cave becomes larger
4-the cave breaks through the headland forming an arch
5-the arch is eroded and collapses
6-this leaves a tall rock stack
7-the stack is eroded forming a stump (may only be seen during low tide)
what is traction
relatively large/heavy rocks are rolled along the seabed
what is saltation
smaller, lighter rocks bounce across the seabed
suspension?
lighter sediment is carried in water
solution?
dissolved sediment is carried in solution
4 ways of marine transport
traction, saltation ,suspension, solution
what does longshore drift do?
builds up a beach
a spit is a ______ ______
depositional landform
what is a spit?
a long narrow feature made from sand or shingle which extends from the land into the sea. form drift aligned beaches
how is a spit formed?
- sand or shingle is moved along the coast by longshore drift,
- sediment will begin to move across the estuary mouth,
- the outwards flow of the river associated with the estuary will stop the spit from forming all the way.
- a secondary wind/wave refraction would carry the sediment around to a more sheltered area forming a recurved spit.
- a salt marsh may develop behind a spit as sediment settles
what type of coastline does a spit form on
discordant
what are the two beach types
swash aligned and drift aligned
describe a swash aligned beach
- sediment moves up and down with little lateral transfer.
- forms in low energy environments
- waves parallel to shore
describe a drift aligned beach
- sediment is transferred along the coast by longshore drift.
- form when waves approach the coast at an angle
- sediment may be graded along the spit*
describe an offshore bar/how its formed
- also known as sandbars
- submerged or partly exposed ridges of sand
- created by waves offshore from the coast
- destructive waves erode sand from the beach with their strong backswash and deposit it offshore
- act as sediment sinks
- can absorb wave energy thus reducing wave impact
a long ridge of sand in shallow water where destructive waves break before reaching the beach.
these waves scour the seabed and throw material forwards into a heap
when are barrier beaches/bars formed
- where a beach/spit extends across two headlands.
behind them, lagoons can form
-formed by longshore drift and deposition
Long strip of sand between ocean and land
what’s a barrier island
when a beach becomes separated from the mainland
long, narrow, offshore deposits of sand or sediments that parallel the coast line.
what’s a tombolow
a beach or ridge of sand that has been formed between a small island and the mainland.
deposition occur where waves lose energy
tomblows may be covered at high tide
-formed by longshore drift and deposition
how many sediment cells are there
and what does this mean
11 in england with them helping the understanding of the coastline through indicating why certain areas may be more vulnerable than others.
what is a sediment cell
has sources, transfers and sinks which are important in understanding the coast as a system. each cell can be regarded as a closed system
what does positive feedback do
amplifies a change in a system so equilbrium is reached
what does negative feedback do
reduces a chaneg in a sytem so equilbrium is reached
example of positive feedback
damaged sand dunes (no grass preventing erosion) so increased source of material
eg of neg feedback
rock fall occurs, protection of cliffs so less erosion so decrease in source of material
3 types of weathering
biological
physical/mechanical
chemical
what does subaerial processes refer to
weathering and mass movement
examples of bio weathering
animals burrowing, roots growing in cracks- cracks then widen(boring molusus)
seaweed acids- seaweed or other marine organisms produce acidic substances that break down rocks along the coast.
examples of chemical weathering
carbonation/acid rain
oxidation
what are rockfalls
occurs when jointed steep rock faces are exposed to mechanical weathering. This causes broken material to bounce vertically down the slope. forming scree-talus
what landforms do rockfalls/blockfalls create
Talus scree slope (material at the base of the cliff that has fallen off.
what are blockfalls
large blocks of rocks falls away from the cliff as a single piece, due to the jointing of the rock
what is soil creep
slowest form of mass movement- almost a continuous process. very small downhill movement of individual particles.
what are 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 flow
slide- material remains intact
flow-material becomes jumbled up
whats rotational slumping
occur in saturated conditions (rotational movement in slumping compared to sliding)
occur on moderate steep slopes
common on softer materials
causes rotational scarps
repeated slumping causes terraced cliff profile
where a section of the cliff remains intact as it moves down a cliff along a curved slip plane.
what are the landforms created by rotational slumping
rotational scars and scarps terraced cliff profile
what are landslides
A landslide is a downwards movement of material, such as rock, earth or debris, down a slope maintaining contact with the cliff surface throughout.
name 2 geological structures
discordant coast and concordant coast
whats a cuspate foreland
whats a cuspate headland
a low lying triangular headland that develops when lsd from two opposite directions forms two spits across a bay
flocculation
a depositional process of tiny clay particles sticking to one another, hence gain enough mass to sink to the river or sea bed.
what is Sediment transportation influenced by
lsd
tides and cuurent
angles of wave attatck
how does vegetation stabilise the coastline
sand dunes and salt marshes
.plant roots bind sediment together so they are less likely to eroded- form yellow dunes(highest point of marram grass)
.plant leaves reduce wind speeds-reducing erosion and deposition
.plants lose leaves become organic material forming soil(salt marsh)
how are sand dunes formed (first stage)
-when there is plentiful supply of sand
-onshore winds blow sand towrads the land
-obstacles such as vegetation to trap sand
-embryo dunes form- collectiong sand and become bigger
-pioneer plants such as sea rocket are able to colonise the stable dunes and help hold/trap more sand
how are sand dunes formed (2nd stage)
-oldest dune closest to land and newest dune closets to the sea
yellow dunes= highest point of marram grass
as these die they produce humus- adding soil fro grey dunes.
these r not fully vegetated and are subject to alteration to wind and waves(blowouts froming gaps in lines of dunes
at high tide/storm conditions seawater may reach dips in psammosere
what is a blowout
a sandy depression in a sand dune env caused by the removal of sediments by wind
what are the types of marine process
erosion
depoistion
transportation
abrasion
HA
attriton
soultion
waves
constructive
destructive
what are the type of physical processes
erosion, mass movement and weathering
what
what are long term features effecting landscapes
geology and sea level
what are short term features effecting landscapes
inputs from rivers
waves (type)
tides
what is dune succession
Nature’s process of building a sand dune
ow
how does salt marshes help stabalise the coast
rivers bring fine mud deposit at side of estruy where flocculation occurs. colonised by algae
pioneer plants survive with brackish water
sediment becomes trapped in roots woth builds us salt marshes height and helps trapping silt during floods-adds new soil from thier decaying vege
what are some depositional processes
- flocculation
- lsd
- constructive waves
4.
what are sources of the sediment cell
and list examples
ersion
- ersion from cliffs
- onshore currents supplying sediment
- land sediment eroded by rivers
- wind blown sediment from land
what are transfers of the sediment cell
and list examples
transportation methods
1. lsd
2. wave trasnfer
3. tides moving sediemnt in and out
4. currents
5. wind along shore
what are sinks of the sediment cell
and list examples
deposion
- backshore- depositional landforms eg sand dunes
- foreshore- depositional landforms
- nearshore-depositional landforms- bars
- offshore
what is a sediment budget
the amount of sediemnt avaible in a sediment cell
