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Why are coastal landscapes different and what processes cause theseā¦
Why are coastal landscapes different and what processes cause these differences? :ocean:
Geological Structure (different scales)
Wave Refraction
:leftwards_arrow_with_hook::ocean::arrow_right_hook:
Deep
water, wave
crests
=
parallel
as water
shallows
towards coast, waves
slow
+ wave height
increases
.
Within
Bays
, wave height
decreases
as the
crests
curve to
fill
the
Bay
.
Straight wave
crests refract
,
concentrating wave energy
on
headlands
as they
curve
.
Powerful
converging
waves concentrated on headland, lower energy -
diverging
waves = within bays.
.
Concordant
High Energy
Erosional
Less resistant rock
=
coves
+ inlets
More resistant rock
=
long offshore islands
(
Dalmatian Coast
, Croatia, Adriatic)
Dalmatian coast
Limestone
geology folded
-->
synclines
+
anticlines
by
tectonic
activity
parallel
to coastline.
1 more item...
Low Energy
Depositional
Offshore bars + barrier beaches
(with lagoons behind) = Haff Coast, Baltic Sea. Slapton Ley, Devon, UK. Chesil Beach, Dorset.
Haff Coasts
Long offshore dune-topped sediment ridges parallel to coastline.
=
lagoons
between
ridges
+
shoreline
. / behind barrier beaches
Rock
strata
parallel to coastline
Discordant
Features
Wave refraction creates:
Stacks
Old Harry Rocks
Stumps
Old Harry Rocks
Bay Head Beaches
(beaches within bays)
Lulworth Cove
Circular bay
with
narrow inlet
Caves
Seven Sisters Caves, Kent
Archs
Durdle Door, Dorset
Coves
Lulworth Cove
Rock strata perpendicular to sea =
differential erosion
Formation of Features
Folds
Layers of rock
deformed
by
tectonic movement
,
pressure
+
heat
.
Lulworth Crumple, Dorset. Created by collision of African + Eurasian plates
Joints
Cracks in layers of rock
in Sedimentary
cracks formed due to ^
pressure
during
formation
of rock
in Igneous + Meta
cracks formed as the
heated
rocks
cool
down
Faults
The two parts of rock have
shifted
along crack due to
tectonic movement
Bedding Planes
Occur in
sedimentary rocks
= composed of layers of
deposited sediment
cemented over time.
Micro
features
Caves
Joints
,
faults
or
bedding planes
exposed +
eroded
to form
sea caves
Blowholes
Erosion along
joint
or
bedding plane breaks surface
further
inland
. Connected to a
cave
. Water forced into cave by
waves
+ forced into
enlarged joint.
Geos
Continued erosion of cave + blowhole = roof collapses creating
narrow steep sided inlet.
.
Dip
Low Angle
SD
Caused by
joints
opened by
weathering
Man O'War Head, Dorset
High Angle
LD
Well developed joints at 90Āŗ to bedding planes
Dungy Head, Dorset
Low Angle
LD
Steep sided stable
cliffs
Uniform Horizontal Layers
Steep sided
cliffs
High Angle
SD
Rock
slabs slide down cliff
along
bedding planes
Features and Landscapes
Background
.
.
Coast as a System
.
Outputs
Sediment
+ water carried to
deep sea
Evaporation
Inputs
Water
+
sediment
from
land
(rivers + cliff face)
Sun's energy
Water
+
Sediment
from
offshore
.
Stores
Coastal
landforms
Sea
Flows
Types of
erosion
Types of
weathering
Types of
mass movement
LSD
Wave refraction
An
open system
in
dynamic equilibrium
Inputs
+
outputs
of
energy
+
matter
.
Factors affecting coast
Atmospheric
Gravity
Solar energy
Climate
+
Weather
Wind direction
,
strength
+
fetch
Human
Tourism
+
Recreation
Sea
defences
Pollution
Building
type
Sea level change
Marine
Salt spray
Wave
size
,
type
,
frequency
+
direction
Tides
- height + range
Local
sea currents
LSD
Depth of
offshore water
Type + amount
of
offshore sediment
Coral Reefs
Sea level change
Terrestrial
Tectonics
Sub-aerial processes
(runoff, weathering, mass movement)
Land erosion
(
glaciers
+
rivers
)
Geology
- permeability, resistance, structure etc.
Rivers
- 90% of sediment to coast
Classification 1
Advancing
Coasts
Land
increasing
relative to sea.
Due to:
^ Deposition =
"outbuilding coast"
Sea level drop + land ^ =
"emerging coast"
Retreating
Coasts
Land
decreasing
relative to sea.
Due to:
Sea level rise + land drops =
"submerging coast"
^ Erosion =
"eroding coast"
.
Classification 5
.
High
Energy
Processes
Erosion
+
Transportation
Sediment source
Eroded
cliffs,
mass movement
,
weathering
(large,
angular debris
),
offshore currents
Landforms
Cliffs, [WCPs, C/A/S/S's]?
Features
Highland + lowland
,
rocky
coasts
Examples
Scotland's Atlantic Coast, Pacific Coasts of Alaska + Canada
Waves
Destructive
, stormy, Long
fetch
Low
Energy
Processes
Deposition
+
Transportation
Sediment source
Rivers
(silt), LSD,
Nearshore Currents
Landforms
Beaches, spits, bars, mudflats, salt marshes, sand dunes
Features
Lowland
coasts,
estuarine
+
costal plains
Examples
East Anglia + Mediterranean
Waves
Constructive
,
Short fetch
Littoral Zone
Onshore
Edge
of land.
Not affected
by sea - affected by
terrestrial
factors
Backshore
Between
HW
mark +
landward limit
, only affected during
storms
.
Intertidal + Nearshore
Shallow
water.
Waves break
here. Used for fishing, trade + leisure.
Offshore + Subtidal
Open
sea.
High
water depth =
little sediment movement
.
Swash Zone
Water up as
swash
, down as
backwash
Surf Zone
Broken waves travel towards shore. Sediment movement on/ off/ along shore.
Breaker Zone
Waves
break here
.
Width
depends on
wave type
.
Classification 3
Primary
Coasts
Dominated by
land-based processes
e.g.
deposition
from
rivers
/ new coastal land from
lava flows
,
weathering
,
mass movement
,
surface runoff
Cliff Profile
Sloped
profile
Low angle
cliff face
Accumulated debris
at
cliff base
Secondary
Coasts
Dominated by
marine processes
Erosion, transport/ deposition processes
Cliff Profile
Steep
,
unvegetated
cliff face
Active
undercutting
Limited debris
at
cliff base
Classification 4
Tidal range
Macrotidal
^ than 4m
tidal range
Tidal activity dominates, ^ affect on coast
Mesotidal
2-4m
tidal range
Tidal action + wave activity important
Microtidal
0-2m
tidal range
Wave activity ^ important than tidal activity.
Difference between HT + LT
.
.
Classification 6
Rocky
Cliffs, WCN, Caves
Stormy
conditions,
destructive
waves
Erosion
, not
deposition
.
Resistant
/ Hard
geology
Abrupt land-sea transition
Steep
relief
Estuarine
(coastal plains)
Low
lying,
covered
at
high tide
-
exposed
at
low tide
Spits, salt marshes, mudflats, beaches
Shallow
offshore
Constructive
waves
Depositional
/ +
Transportation
Soft
geology
Sediment
from
offshore
(beach) +
rivers
(salt marsh)
Gradual transition land-sea
Mouth
of
rivers
e.g. Hampshire
Factors affecting recession
Vegetation
UK
Estuarine
Coastlines
Salt marshes
develop from
coastal
+
river sediments
Halosere Succession
Formation
Low energy
environments
Tides bring
sediment
+ rivers deposit
silt
Clay particles
stick together via
flocculation
, ^ weight +
settle
1 more item...
Found behind
bays
/
spits
/
estuaries
Sandy Coastlines
Sand Dunes
Onshore
wind
Sediment trapped by strand line = embryo dune
Pioneer species
e.g. sea rocket (
xerophytes
) tolerate
salinity
.
Pioneer species
die
=
humus
= pH reduced
Pioneer
roots stabilise
sand -- other plants
colonise
(Marram, Sea Couch) =
yellow dunes
1 more item...
Psammosere Succession
Tropical Places
Mangrove
forests
Bangladesh
Trap sediment
Coral reefs
Protection
from
wave action
+
storms
Great Barrier Reef
Lithology
Factors Affecting Lithology
Origin of Rock
Igneous
Very slow
erosion
Sedimentary
Moderate-Fast
erosion
Limestone
May have
bedding planes
,
joints
or
faults
Metamorphic
Slow
erosion
Glacial Till
Very fast
erosion
Cohesiveness of Rock
Consolidated
Erosion
resistant
- cemented together
Unconsolidated
Erosion
vulnerable
- sand, gravel, clay etc.
Glacial Till at Holderness
Permeability of Rock
Permeable
Limestone
Pervious
- water can pass through
joints
,
faults
etc.
Chem susceptible
to
carbonic acid
via rain = pitted
Chalk
Porous
- allows water in, but cannot filter out. ^ risk of
freeze thaw weathering
.
Impermeable
Granite, clay
Impervious
.
Permeable
rock overlies
impermeable
rock =
mass movement
e.g.
slumping
+
rock slip
can occur.
Wave Type
Constructive
Spilling breaker
=
backwash percolates
through
sediment
Destructive
Crest
moves
forward + downwards
+ enclose
air pockets
while
plunging
95%