Coastal landscapes (P1- SEC C) Flashcards
what are constructive waves?
LOW WAVES and LONG WAVELENGTH that surge up the beach and ‘spill’ with POWERFUL SWASH.
- carries/deposits large amounts of pebbles/sand to CONSTRUCT THE BEACH
what are destructive waves?
Formed by local storms close to coast
CLOSELY SPACED
HIGH/STEEP WAVES that PLUNGE INTO BEACH
LITTLE SWASH but POWERFUL BACKWASH - removes sand/pebbles so ‘destroys’ it
what is the FETCH?
how far the wave has travelled
attrition?
rock fragment carried by the sea knock against each other causing small/more rounded rocks.
abrasion?
‘sandpapering’ effect on pebbles grinding over a rocky platform - becomes smooth
solution?
dissolving of soluble chemicals in rocks
corrasion?
fragments of rocks are picked up/hurled by the sea at a cliff.
the rocks erode the cliff
hydraulic power?
POWER of waves as they smash onto the cliff. trapped air is forced into cracks In rocks making them break - cavitation
5 main processes that influence shape of the coastline?
EROSION
WEATHERING
MASS MOVEMENT
TRANSPORTATION
DEPOSITION
weathering?
weakening or decay of rocks in their original place on, or close to , the ground surface
2 types of physical weathering and explain?
freeze thaw - water collects in cracks of rock and freezes/expands making cracks bigger
- when temps rise, ice thaws , water seeps deeper into rocks
REPEAT - THEY BREAK
Salt weathering - seawater evaporates leaving CRYSTALS
- they grow/expand
- put pressure on rocks /breaks
chemical weathering ?
rainwater absorbs co2 from air and becomes acidic
- contact with alkaline rocks causes CHEMICAL REACTION , so rocks DISSOLVE
mass movement ?
downward movement or sliding of material under influence of gravity
types of mass movement?
ROCKFALL - rocks break away from cliff face often due to free thaw weathering
ROTATIONAL SLIP- slump of saturated soil/weak rock along a CURVED surface
MUDFLOW- saturated soil/weak rock flow down a slope
LANDSLIDE - blocks of rock slide downhill
coastal transportation - 4 ways ?
solution ; dissolved chemicals from limestone and chalk
suspension: particles carried in water
traction ; large pebbles rolled along a seabed
saltation ; a ‘bouncing’ motion of particles too heavy to be suspended
describe and explain the process of longshore drift?
- process where waves transport material
-the swash moves material up the beach at an angle - the material the moves back at 90 degrees due to gravity
- this movement carries on along the beach in a zig-zag motion
what types of rock form bay and headlands?
weaker rocks erode to FORM BAYS
tougher rocks erode SLOWER to form HEADLANDS
How do wave cut notches and platforms form?
when sea attacks base of cliff, erosion wears away the cliff at the base forming WAVE CUT NOTCH
overtime the notch gets DEEPER by corrasion, hydraulic action, abrasion /UNDERCUTS THE CLIFF - eventually the overlaying cliff can supports its weight/collapses
- as sequence continues cliff retreats and form a gentle sloping platform - WAVE CUT PLATFORM
how are caves , arches and stacks formed?
- crack in headland made larger by hydraulic action AND GROWS INTO CAVE
- cave breaks though headland forming arch
- base of arch becomes Widder and thinner through erosion and weathering/ roof of arch collapses leaving stack
how do beaches form?
DEPOSITION OF SAND /SHINGLE
- waves are constructive
- pebble beaches formed by high energy environments as they wash away fine sand and leave large pebbles
how do sand dunes form?
SAND DEPOSITED on th beach and blown INLAND by wind to form dunes.
- stabilised by vegetation to form FORE DUNES/YELLOW DUNES
HOW DO SPITS FORM?
- forms where there is ALOT of LONGSHORE DRIFT , where coastline suddenly changes shape
- SEDIMENT DEPOSITS out to sea and builds up - forms EXTENSION OF LAND
- this continues making it more extended until water becomes too deep
- strong winds /tidal currents causes CURVED END SPIT
HOW DO BARS FORM?
longshore drift can cause SPIT to grow ACROSS A BAY! - TRAPS LAKES BEHIND IT -BAR
CASE STUDY : SWANAGE , location , landforms
Seaside town in DORSET , SOUTH COAST OF UK
-located in a sheltered bay/broad sandy beach , between 2 headlands
SWANAGE BAY - because sand and chalk between the two bands of hard resistant rock erodes at a faster rate.
N of swanage - POOLE HARBOUR
- increased DEPOSITION at mouth of several rivers
- formed large esturary/salt marsh
why do coasts need to be managed?
MAINTAIN balance between forces of nature and demands of people
what are 3 management strategies ?
HARD ENGINEERING - use artificial structures to control natural processes
SOFT ENGINEERING - less intrusive, envrironmentally friendly method that wrks with natural processes
MANAGED RETREAT- allowing the sea to flood over low lying land
HARD ENGINEERING - GROYNES
ad and dis
TIMBER /rock structures built out to sea from the coast - trap sediment/enlarge beach
- wider beach is buffer to reduce wave damage
- stop material being moved along beach by longshore drift , as sand builds up on updrift side
AD : wider beach - tourism
- provide useful structures for fishing
- not too expensive
DIS:
- unattractive
- deprives areas downwind of sediment, increasing erosion elsewhere
HARD ENGINEERING - SEA WALL
AD/DIS
Concrete/rock barrier against the sea at foot of cliffs /at top the beach
- absorb/deflect energy of waves back to sea
AD :
- effective
- has walkway
DIS : can look obtrusive/unnatural
- expensive
HARD ENGINEERING - ROCK ARMOUR
AD/DIS
Piles of large boulders dumped at foot of cliff. the rocks force waves to break , absorbing energy , protecting cliffs .
- gaps between rocks , disperses energy of waves - decrease erosional power
AD: cheap
- used for fishing
DIS :
- rocks are from elsewhere so doesn’t fit in with local geology
- obtrusive
HARD ENGINEERING - GABIONS
AD/DIS
wire cages filled with rocks to support a cliff/buffer against the sea
AD : cheap
improve cliff drainage
DIS : look unattractive
only last 5-10 yrs
SOFT ENGINEERING - BEACH NOURISHMENT
AD/DIS
addition of sand /shingle to existing beach to make it higher water
AD: cheap/easy to maintain
blends in
increase tourism
DIS : needs contrast maintenance
what is reprofiling ?
- artificial reshaping of a beach using existing beach material.
SOFT ENGINEERING - DUNE REGENERATION
AD/DIS
sand dunes buffer the sea . MARRAM GRASS is planted to stabilise dunes/help them develop
AD : maintain natural environment
- cheap
DIS : planting is time consuming
easily damaged in a storm
HARD ENGINEERING - REVETEMENTS
AD/DIS
wooden and concrete ramps that helps absorb wave energy
AD: Cost effective
DIS : unattractive
need constant maintainance
what is managed retreat?
deliberate policy of allowing the sea to flood or erode an area of relatively low land.
reasons for management , management strategies and the future of MEDMERRY MANAGED RETREAT?
REASONS : protected by LOW SEA WALL that needs repair /protect against rising sea levels
STRATEGIES : allow the sea to breach sea defences /flood farmland
cost : 28 mill in NOV 2013
FUTURE: - create a large natural saltmarsh
- help protect surrounding farmland /caravan parks from flooding
- establish wildlife habitat /encourage visitors
example
Lyme Regis - issues
- town is on UNSTABLE CLIFFS
- coatsline eroding rapidly -> properties destroyed/damaged
example
Lyme Regis - how is it managed?
lyme Regis Envrionemental Improvement Scheme
- new sea wall/promenade -
- creation of wide sand/shingle beach
- extension of rock armour
Lyme Regis - how successful was scheme?
POSITIVE OUTCOMES
- have business thriving on seafront
- defences withstand stormy winter
- harbour is better protected
NEGATIVE OUTCOMES
- more visitors –> more conflict/traffic
- defences spoil natural landscape
