Coasts 2 Flashcards
EROSIONAL LANDFORMS
strata - how is horizontal strata affect the shape
- undercutting leads to riockfall
EROSIONAL LANDFORMS
strata - how is seaward sipping strata affect the shape
- undercutting leads to undercutting which removes support, rock laters loosened by weathering and slide down
EROSIONAL LANDFORMS
strata - how is landward dipping strata affect the shape
- undercurring leads to loosened rock thats difficult to dislodge, bot overtime slope profile is lowered by mass movement
EROSIONAL LANDFORMS
subarial processes include
weathering
freeze thaw
salt crystalisation
thermal expansion
chemical
EROSIONAL LANDFORMS
shore platforms
regular removal of debris at the foot of the cliff cause what
the cliff profile remains steep
EROSIONAL LANDFORMS
shore platform
process of shore platform
- sea creates a wave sut notch
- weathering occours at the top of the cliff, causing it to collapse
- constructive waves transport material away reating a shore platform
EROSIONAL LANDFORMS
shpre platform
a level 4 points
- sediment being dragged away causes erosion of shore platfrom
- before this shore platform must reach width of 500m
- solution occours due to algea releacing co2 at night time, means co2 in water = carbonation
- between 0-3 degress, as wave levels are most consistant at high and low tide, so erosion is highest at these points leaving a low level ramp anf wave cut notch
EROSIONAL LANDFORMS
wave refraction
name of waves
orthogonals
EROSIONAL LANDFORMS
wave refraction
what happens to headlands
- converging orthogonal waves concentrate on headlands, due to bein frefracted with hig energy = high erosion
EROSIONAL LANDFORMS
wave refraction
what happens energy
energy is dissipated for bays
EROSIONAL LANDFORMS
wave refraction
what happens to bays
- bays have diverging orthogonal waves causing deposition due to low energy
EROSIONAL LANDFORMS
blow holes and geo
how are blow holes formed
splashing of waves englarges joints into a cave, air is trapped inside, overtime a natural shaft is formed when it breaks through surface
EROSIONAL LANDFORMS
blow holes and geo
how are geos formed
enlargement of blow holes weakens cave roof and overtime collapses
EROSIONAL LANDFORMS
blow holes and geo
3 a level points
- starts at wave cut notch
- hard rock - needs strength and structural integrity for caves and creeks
- needs structural weaknesses ( complex ) to allow vertical erosion
DEPOSITIONAL LANDFORMS
where does deposition most commonly occur ( 5 )
- when accumulation exceeds rate of removal
- when waves slow immediately after braking
- at the top of the wash when water is no longer moving
- during backwash when water percolates into the beach
- low energy sheltered areas
DEPOSITIONAL LANDFORMS
What’s settling velocity
The velocity at which particles are deposited - heavy first
DEPOSITIONAL LANDFORMS
How does a gentle gradient beach occur
- Less then 5°
- small particles become compact when wet
- allows little perculation during backwash
- little energy is lost to friction and little volume is lost during percolation = gentle gradient
DEPOSITIONAL LANDFORM
How does steep beaches occur
- larger sediment
- wash is stronger then backwash so there is a November of shingle on shore
- makes the upper part of beach where rapid percolation occurs due to larger air spaces
DEPOSITIONAL LANDFORMS
Particle size and beach angles ( 2 )
Pebbles - 4mm. 17°
Medium sand - 0.2mm. 5
DEPOSITIONAL LANDFORMS
Beach features ( ripples, storm beach, runnels and cusps )
Ripples - loose sandy seabed is subject to wave action and ripple marks appear - TIDAL
Storm beach - accumulation of large sediment above high water mark due to storm action 1-100 YEARS
Runnels - with ridges being areas of raised beach, the dips are water filled troughs actin f as draining routes for tides TIDAL
Cusps - sand and gravel deposits in an arc patterned formed by wave patterns of converging currents TIDAL
DEPOSITIONAL LANDFORMS
Difference between summer beaches and winter beaches
Summer - more gradual slope due to smaller waves trying to replace sediment lost during winter
Winter - Steeper due to storm conditions
DEPOSITIONAL LANDFORMS
What’s a swash aligned beach
Beach breaking parallel to the shore = move member of sediment being up and down = Bay head beaches
DEPOSITIONAL LANDFORMS
What’s a drift aligned beach
Drift aligned beaches develop when waves approach at an angle, process of LSD
DEPOSITIONAL FEATURES
How do spits form and example
- formed by LSD occurring on the dominant prevailing wind direction
- sediment carried and deposited at low energy and shallow areas when settling velocity is reached
- can be recited by change in wind direction
- leeward side = salt marsh due to low energy
EG
Orford ness = east angkia
- north easterly winds dominant
DEPOSITIONAL FEATURES
how are bars formed and example
- Low energy environment, shallow area, settling velocity reached = deposition
EXAMPLE
Spurn head = Humber estuary
DEPOSITIONAL FEATURES
How are tombolos formed and example
- accretion of sand at the Lee of the island = low energy
- formed via wave refraction due to shallow water
- Convergence of LSD = meets around island at Lee = settling velocity reached
EXAMPLE
St ninans = Shetland
DEPOSITIONAL FEATURES
chelsil beach 1st theory
LSD
DEPOSITIONAL FEATURES
CHESIL BEACH 2nd theory
- last glacial period = sea was 120m lower
- many rivers flowing from mainland
- barrier island formed via fluvial deposits
- sea levels rise after glacial period - barrier island is forced to migrate and is now wedged where it is
DEPOSITIONAL FEATURES
Evidence for 2nd theory of chesil beach
- When barrier island formed - sediment is evenly distributed
- when it moved the primary LSD transported all sediment south
- secondary weaker LSD transported smaller sediment north
CHESIL BEACH HAS SMALL SEDIMENT FIRST = unusual as it’s always LARGE - SMALL
EAST YORKSHIRE COASTLINE
geology of FH, SB,FBrigg
hard lithology - chalk and limestone
complex structure - bedding planes and faults
EAST YORKSHIRE COASTLINE
FH, SB,FBrigg - rate of erosion
0.1m/year
EAST YORKSHIRE COASTLINE
FH, SB,FBrigg, common mass movement ?
rockfall
EAST YORKSHIRE COASTLINE
what type of coastline and what does this cause
disconcordant = differental erosion
EAST YORKSHIRE COASTLINE
RHB,FB, - geology
soft lithology = sandstone, mudstone and clay
complex lithology = bedding planes and faults
EAST YORKSHIRE COASTLINE
Rate of erosion for RHB,FB
0.8m/year
EAST YORKSHIRE COASTLINE
RHB,FB type of mass movement
slumping = rock permeable
EAST YORKSHIRE COASTLINE
Physical factors ( wind )
0-gale force = frictional drag imparting energy onto waves over a long period of time due to 1500km fetch
50kg/cm2 of pressure
EAST YORKSHIRE COASTLINE
physical factors ( tide )
neap tide 4.8m
ebbing tide 6.1 - salt crystalisation
EAST YORKSHIRE COASTLINE
physical factors ( temp )
- rarely below freezing, not to hot
- rarely freeze thaw and chemical weathering
- storm cause destruction
EAST YORKSHIRE COASTLINE
F head north side
- waves concentrated
- erosional features due to marine actlivites
EAST YORKSHIRE COASTLINE
F head south side
- waves disperced
- depositional featers eg: north shore beach
- lower setting velocity and more constructive waves
EAST YORKSHIRE COASTLINE
inter relationships
physical factors - geomorphic processes - coastal features
EAST YORKSHIRE COASTLINE
temporal features
tide - daily
- beaches 100s of years
- equilibrium regained after storm Bech after years
- seasonal changes = more destructive waves in winter
- mass movemnt is seconds
EAST YORKSHIRE COASTLINE
example of mass movement
- holbeck hall landslide example
- 60m of glacial till lost overnight = soft rock
NILE DELTA
Why did they build the Aswan high dam and the affects
- natural floods leaving silts = fertile ground
- built yhe dam to control the flooding because more floods = more agriculture
- traps 98% of sediment = impacts dynamic equilibrium
- lake nassa behind = sediment deposited sue to low energy environment = less sediment in delta = more erosional
NILE DELTA
Key facts
6650km long
4.26 t/ha/y = sediment input
Originates in Ethiopia
NILE DELTA - physical factors
Waves
- short fetch, enclosed sea, higher wave height by 1m in winter = constructive waves
- LSD occurs pulling sediment creating smaller scale drift aligned features which make up front of delta
NILE DELTA - physical factors
Wind
NW wind 10mph , higher in winter
W-E sediment drift
Aeolian brings sediment from ly Ian desserts
NILE DELTA - physical factors
Geology
- Delta made up of soft lithology ( alluvial silts )
- limestone ridges on Alexandra = formation of Abu quir headland and bay
NILE DELTA - physical factors
Tides
- Very low tidal rand which is important for delta formation
- low tidal range as most sediment is brung in via fluvial inputs
NILE DELTA - physical factors
Ocean currents
Very insignificant but help LSD
Now more significant due to less sediment output from fluvial sources = more sediment from lybia
NILE DELTA - physical factors
Sea level rise
10-15 cm rise has meant a 10-15m retreat
If sea level rises 1m it’s predicted that 15% of the delta will be lost
Sea level rises means: increased energy, wave height and tidal range. More marine processes changing it from depositional to erosional
NILE DELTA - Features
Rosetta and Damietta promentry
- deposition due to flocculations when clay hit the Mediterranean
- NW wind = exposed to strinf destructive waves = sediment imput
- the sediment is dragged along the edge of delta and deposited in the low energy environments = spits and drift aligned features
- now overall more of an erosional environment due to lack of sediment
NILE DELTA - Features
Bulurus and manzala lagoon
- LSD and ocean currents move sediment W-E due to NW wind
- sediment moved to delta front = deposition in low energy environments
-lagoons getting smaller due to bars preventing the lagoons access to sea, therefore evaporation due to hot environment
- increases erosion = lack of sediment
NILE DELTA - Features
Abu quir headland and bay
- limestone ridges = headland and soft rock = bay
- differential erosion and diverging waves
NILE DELTA - Features
Sand dunes
- onshore winds blowing sediment
- aeolian transport from neighbouring sediment
DEPOSITIONAL FEATURES
SALT MARSH
where do they form
what conditions needed for formation
- low energy environments eg: estuarys
- little wave action, shelter from exposure, source of sediment
DEPOSITIONAL FEATURES
SALT MARSH
formation
- clay particles arrive through fluvail imputs via suspension
- only 0.05mm so too light to settle, flocculation occours where the electrical charge from clay is wiped by sea water, therefore can clump together and settle
DEPOSITIONAL FEATURES
SALT MARSH
zonation and sucession
- zonation is a spatial pattern, different species have different abiotic factors and are loacted in areas where they can withstand salt
- halophytes are in lower areas as they are reguarly submerged due to having a high tolerance
- sucession is when a new species emerges, this occours at areas with little salt tolerance due to large competion
DEPOSITIONAL FEATURES
SALT MARSH
factors affecting
- changes in wave size can alter marsh stability
- chnages in tides alter species location ( zonation )
- costal squeeze - as its a dynamic environment when the sea levels rise the marsh moves to accomodate for species with a low salt tolerance, if hard engineeding occours it cant migrate = costal squeeze
DEPOSITIONAL FEATURES
Deltas
what are they
- formed when rivers empty their water and sediment into an alternate body of water
- occours in low energy environments with a large sediment load
DEPOSITIONAL FEATURES
Deltas
distributaries
levees
crevasse spray
distributaries - branch of into smaller streams
levees - these are built up areas of sediment surrounding distributaries
crevasse cpray - fluvial deposits when a levee breaks
DEPOSITIONAL FEATURES
Deltas
3 types
cuspate delta = pointed extension when sediment accumulates due to alternating gentle currents
eg : timber river in Rome
arcuate delta = sufficient sediment supply, grows seawards eg: nile delta
Birds foot delta - distributaries not reaching coast due to sediment supply being more then sediment removal
