Unit
5:
Coastal
Environments
Coast-‐
a
narrow
contact
zone
between
land
and
sea
It
is
dynamic
so
constantly
changing
due
to
effects
of
air,
land
and
marine
processes
Waves-‐
(main
forces
changing
shape
of
any
coastline)
caused
by
the
friction
of
the
wind
on
the
surface
if
the
water.
Height
and
strength
of
waves
depends
on:
Ø The
speed
of
wind
Ø The
length
of
time
the
wind
blows
for
Ø The
length
of
water
the
wind
blows
over
Fetch-‐
the
distance
(length
of
water)
the
wind
blows
over
Stronger
the
wind,
larger
the
wave
Greater
the
fetch,
larger
the
wave
E.g.
waves
along
north
coast
large
as
wind
comes
from
Atlantic
(America)
How
do
waves
interact
with
coastline?
Ø As
wave
approaches
coast,
its
lower
section
is
slowed
more
than
the
upper
sections
due
to
friction
from
seabed
or
beach
Ø Upper
section
of
wave
reaches
a
crest
and
topples
over
(breaks)
and
either
hits
a
cliff
or
surges
up
the
beach.
Swash-‐
movement
of
the
wave
up
the
beach
Backwash-‐
as
the
wave
retreats
back
down
the
beach.
The
dynamic
nature
if
coast
is
due
to
two
types
of
wave:
destructive
and
conservative
Destructive
waves-‐
plunging
waves
which
occur
mostly
on
steeply
sloping
beaches
and
then
erode
the
beach
because
the
backwash
is
stronger
than
the
swash
(erode
coastline)
v Occur
on
steeply
sloping
beaches
v High,
steep
waves
so
when
they
break
the
water
crashes
down
on
the
beach
v They
arrive
at
rate
of
13-‐15
per
minute
v Stronger
backwash
than
swash,
so
pull
material
from
beach
and
erode
coastline,
changing
its
dynamic
shape
v Dangerous
because
can
arrive
very
quickly
and
one
after
other,
the
backwash
has
to
slow
under
incoming
wave.
This
flow
is
called
a
rip
current
and
can
drag
swimmers
out
to
sea.
Constructive
waves-‐
spilling
waves
which
occur
mostly
on
sloping
beaches
and
deposit
material
further
up
the
beach
because
the
swash
is
strength
than
backwash
v Occur
on
gently
sloping
beaches
v Low
waves
so
when
they
break
the
water
runs
gently
up
the
beach
v Arrive
at
rate
6-‐8
per
minute
v Have
strong
swash,
so
push
material
up
beach
v As
swash
is
stronger
than
the
backwash,
material
is
carried
onto
land
and
deposited,
changing
dynamic
shape
Coastal
processes
Just
like
a
river,
sea
erodes,
transports
and
deposits
material.
Unlike
river,
sea
has
much
greater
force
and
can
move
material
all
round
the
globe.
Coastal
erosion
(CASH)
Corrasion/abrasion-‐
the
force
of
moving
water
in
the
sea
throws
stones
and
other
eroded
particles
that
it
is
carrying
against
the
coastline
and
cliffs,
which
Seabed
NOT
river
bed
dislodges
ore
material.
Attrition-‐
particles
already
eroded
from
rocks
and
cliffs
that
are
transported
by
the
sea
hit
against
each
other,
reducing
their
size
and
making
them
more
rounded
Solution/
corrosion-‐
seawater
contains
salts
and
acids
that
can
dissolve
away
the
rocks
from
the
seabed
or
cliffs.
This
process
is
most
effective
on
limestone
coasts
when
calcium
carbonate
is
dissolve
and
can
create
spectacular
caves.
Hydraulic
pressure
(action)-‐
waves
force
water
and
air
into
cracks
in
the
rock.
The
parcels
of
air
can
be
compressed
by
surging
water,
then
expand
explosively,
breaking
up
the
rock
in
the
cliffs.
Coastal
transportation
Just
like
rivers,
sea
transports
material
(saltation,
suspension,
solution,
traction).
Longshore
drift-‐
the
movement
of
material
along
the
beech
in
a
zigzag
route
, 1. Waves
approach
the
beach
at
a
slight
angle
2.
As
the
waves
break,
the
swash
carries
material
up
the
beach
at
same
angle
waves
approached
3. As
swash
dies
away,
the
backwash
and
any
material
carried
by
it
falls
straight
back
down
the
beach
under
influence
of
gravity
4. This
means
material
is
moved
along
the
beach
in
a
zigzag
route.
• On
south
coast
of
England
material
moves
from
west
to
east
because
prevailing
wind
is
from
southwest.
• Longshore
drift
is
link
between
erosion
and
deposition
along
coast-‐
eroded
material
transported
then
deposition
further
along
coast.
Coastal
deposition
Ø Load
of
seas
and
oceans
build
up
on
coastline
to
form
beaches,
spits
and
dunes.
Ø This
material
is
added
by
constructive
waves
Ø Deposition
occurs
during
light
winds
and
when
flow
slows
down,
has
less
energy
and
drops
sediment
Ø Summer
is
most
common
for
deposition
while
erosion
dominated
winter
in
UK.
Coastal
landforms
Erosional
landforms:
headland,
cliffs,
wave
cut
platforms,
caves,
arches
and
stacks.
Headlands-‐
areas
of
land
along
the
coast
that
extent
out
to
sea
and
are
usually
higher
than
the
surrounding
land.
Forms
when…
1. Bands
of
hard,
resistant
rock
(e.g.
basalt)
and
soft,
less
resistant
rock
(e.g.
limestone)
are
found
in
same
coastal
area
2. Destructive
waves
erode
softer
rock
faster
than
more
resistant
rock
3. The
harder,
resistant
rock
is
left
sticking
out
to
sea
while
the
soft
rock
erodes
into
a
bay
where
sand
will
be
deposited
E.g.
Fairhead
headland
near
Ballycastle,
Durlston
head,
near
Swanage,
England
Cliffs-‐
a
vertical
rock
face
along
a
coast
Formation…
1. Shape
of
cliff
determined
by
rock
type
(geology)
2. Type
of
rock
determines
how
resistant
it
is
to
erosion,
and
way
layers
(strata)
of
rock
are
angled
can
determine
shape
of
cliff
3. If
rock
is
hard,
tall,
dramatic
cliffs
can
form
that
are
more
resistant
to
erosion.
E.g.
cliffs
of
Moher,
County
Clare,
Ireland
4. If
rock
is
soft,
such
as
made
of
boulder
clay,
erosion
will
be
faster
and
the
cliff
will
wear
away
more
quickly.
E.g.
Holderness
coast,
England
Wave
cut
platforms-‐
a
narrow,
flat
area
of
rock
normally
found
at
the
base
of
a
cliff,
formed
due
to
erosion.
Formation…
1. Corrosion
and
Hydraulic
action
through
wave
action,
cut
a
notch
at
the
base
of
cliff-‐
creating
point
of
weakness
2. Rock
above
the
notch
is
undercut
and
a
section
of
cliff
breaks
off
3. Rubble
collects
at
foot
of
cliff
and
will
get
removed
by
attrition
4. This
repeats,
the
cliff
wears
back
and
a
wave
cut
platform
develops
underwater,
which
you
can
see
at
low
tide.
As
cliff
is
worn
back
further,
the
wave
cut
platform
gets
wider.
Caves,
arches
and
stacks
Cave-‐
joints
and
cracks
are
eroded
by
waves
to
form
large
gaps
in
the
cliff
Formation…
1. Many
rocks
in
cliffs
(e.g.
limestone)
contain
faults
and
joints.
2. These
areas
of
weakness
will
be
opened
up
by
waves
pounding
at
the
cliff
and
minerals
will
dissolve
(corrosion).
3. Air
gets
compressed
in
the
cracks
and
they
may
enlarge
through
hydraulic
pressure.
4. Over
time
cracks
get
so
big
they
become
caves
Arch-‐
a
hole
that
extends
right
through
a
cliff
headland
Formation…
