1.1.1 Out at sea, the wind tugs at the
surface of the water, causing the wave
shape to move. From this moment on,
the water moves forward. When a
wave moves into shallow water near
the coast, it is distorted until it breaks.
220.127.116.11 A wave crest is the point on a
wave with the maximum value
or upward displacement within
18.104.22.168 A wave trough is the minimum
or lowest point within the a
1.1.2 Water rushes up the beach - this is called the swash
1.1.3 After it has rushed up the beach, it then drains back down the beach. This is known as the backwash.
1.1.4 What makes a
22.214.171.124 Stronger winds
126.96.36.199 Distance wind has travelled (fetch)
188.8.131.52 More time wave has travelled for
1.2 Constructive Waves
1.2.1 These have a strong swash and a weak backwash.
This means that the beach is filled with material, because
the backwash is not strong enough to remove it.
1.2.2 They are
low & long.
1.3 Destructive Waves
1.3.1 They are
1.3.2 These have a weak swash and a
strong backwash. The backwash pulls
pebbles & sand down the beach
when the water retreats, removing it.
2 Types of erosion
2.1 The wearing away
of land by the sea.
2.1.1 Destructive waves hit the original coast line,
eroding the rock with its sheer force. Because
this type of wave has a strong backwash, it
pulls the crumbled rock, removing it from the
beach and causing the cliff to retreat.
2.2.1 This is the force of the
bits of rock carried in the
water blasting into the
cliff. Bits of rock & sand in
waves grind down the cliff
surface like sandpaper.
2.3.1 This is a chemical reaction
between the sea water & the
minerals in the rocks. Acids
contained in sea water will
dissolve some types of rock
such as chalk or limestone.
2.4.1 This is the process of rocks hitting
each other & breaking into smaller
rocks. Waves smash rocks & pebbles
on the shore into each other & they
break & become smoother.
2.5.1 This is the force of water hitting the cliff &
squeezing air into cracks in the rock. Air
may become trapped in joints & cracks on
a cliff face. When a wave breaks, the
trapped air is compressed which weakens
the cliff and causes erosion.
3 Features or erosion and their formation
3.1 Lines of weakness
such as faults occur in
and hydraulic action
erode the fault to form a
cave. The cave is
deepened. The sea cuts
through to form an arch.
The sea erodes the foot
of the arch and widens
it. The roof of the arch
becomes too heavy and
collapses. Part of the
former cliff is now
isolated as a stack. Over
time the stack is
undercut and collapses.
A stump is the remains
of the eroded stack.
eroding the cliff.
3.1.2 Destructive waves are involved in this
process, because of their strong
backwash of pulling material away.
4.1 The movement of
sediment load by the sea.
4.2.1 Larger pebbles and cobbles are rolled along the sea bed.
4.3.1 Small pebbles are moved when one pebble hits
another, causing it to bounce. This bouncing
can set up a chain reaction.
4.4.1 Dissolved material is carried along
in solution, so you can't see it.
4.5.1 Fine sediment is carried as a suspension in
the water, making it look muddy or murky.
5 Longshore drift & spit formation
5.2 A spit is an accumulation of sand with one end attached
to the land & the other reaching out across an estuary
or into the sea. They are features of coastal deposition.
5.3 Spits are formed when large amounts of
sediment are transported by longshore
drift & where the coastline suddenly
changes direction to leave a sheltered,
shallow area of water. Due to an increase
in friction, more deposition can occur in
the water sheltered by the headland.
5.4 Sediment is moved diagonally by the
swash & backwards by the backwash. If
there is a river estuary, longshore drift
continues to transport the sediment.
However, the river current is too strong
for longshore drift to reach the other side
of the estuary. Secondary winds create a
hook shaped curve on the end of the spit.
5.5 Behind the spit is very sheltered. Here a salt marsh forms.
6 Mass movement
& cliff collapse
6.1 When rocks loosened by weathering
move down slope under the influence of
gravity. The rocks can slide or slump.
6.2 Physical causes of it: rain, type
of soil, waves, weathering.
6.3 Human causes of it: building,
watering, planting, tourism.
7 Coastal Defence
7.1 Hard Engineering
7.1.1 Sea wall
184.108.40.206 Effective, walkway.
220.127.116.11 Unnatural, expensive.
18.104.22.168 Tourist & fishers attraction.
22.214.171.124 Unnatural & interrupts longshore drift.
7.1.3 Rock armour
126.96.36.199 Cheap, provides interest.
188.8.131.52 Obtrusive, hard to transport.
7.2 Soft Engineering
7.2.1 Sand dune regeneration
184.108.40.206 Natural, cheap,
popular for wildlife.
220.127.116.11 Easily damaged,
7.2.2 Managed retreat
7.2.3 Marsh creation
18.104.22.168 Cheap, habitat
22.214.171.124 Lost land.
7.2.4 Beach nourishment
126.96.36.199 Constant maintenance needed.
7.3 Destructive waves erode
the bottom of the cliff,
causing it to retreat.
Coastal defence slows the
process of erosion down.
8 Case Studies
8.1 Holbeck Hall
8.2 Hurst Castle Spit
8.3 Old Harry Rocks
9.1.1 When rain water reacts with minerals in rock and forms soft clay.
9.2 Mechanical /Physical
change (rock falls
away like skin),
off), wind, rain &
9.3.1 Where plants roots
grow & make cracks in
rook larger. Or when
creatures walk /dig etc.