Transcript COASTAL PROCESSES

COASTAL
PROCESSES
COASTAL
PROCESSES
COASTAL
EROSION
COASTAL
TRANSPORTATION
COASTAL
DEPOSITION
COASTAL
DEPOSITION
It refers to processes that results in the addition of materials
to the coasts.
COASTAL TRANSPORTATION
This refers to the movement of materials along the coast.
COASTAL
EROSION
This refers to the processes that results in the removal of
materials from the coasts.
COASTAL EROSION
COASTAL EROSIONAL
PROCESSES
HYDRAULIC
ACTION
FACTORS AFFECTING EROSION
WAVE SIZE
ABRASION/
ROCK COMPOSITION/
CORRASION
STRUCTURE
ATTRITION
POSITION OF COAST
SOLUTION/
CORROSION
CLIMATE
COASTAL
EROSIONAL
PROCESSES
HYDRAULIC ACTION I
Waves repeatedly hits against soil and rocks along a coast.
Over time, the repeated wave action loosens these soil and rocks and
sweeps them away.
This process is known as hydraulic action.
HYDRAULIC ACTION II
As the waves pound against the coast, the air within these cracks is
compressed.
When the waves recede, the compressed air suddenly expands.
Over time the repeated compression and expansion widens and
weakens cracks and ultimately breaks the rocks.
ABRASION
Waves carry rock fragments such as pebbles and gravel.
These fragments act as chiselling tools when they are hurled against
the coast, and breaks the rocks.
This process is known as abrasion.
ATTRITION
Rock fragments carried by the waves are thrown against one another.
This gradually break up the rocks into smaller, smoother and
rounded pieces.
This process is known as attrition.
SOLUTION
Soluble minerals in coastal rocks are dissolved in and removed by the
seawater.
For example, calcium carbonate reacts chemically with the carbonic
acid and changes into soluble hydrogen carbonate.
When solution occurs, the rocks are weakened and ultimately
disintegrates.
FACTORS AFFECTING
COASTAL EROSION
WAVE SIZE
The bigger the waves, the more energy they have to erode the coast.
This is because larger waves have more powerful backwash than the
smaller waves that plunges over when breaking.
This erodes the coast faster.
ROCK COMPOSITION I
Soft rocks such as shale and clay will be eroded faster than hard rocks
such as granite and basalt.
This is because, such rocks being weaker are unable to withstand the
force of the strong waves.
ROCK COMPOSITION II
Similarly, rocks with mineral composition that that or chemically
react with water to form new chemicals are more prone to erosion.
This is because, such rocks are gradually weaken under the constant
attack of sea water and break down.
ROCK STRUCTURE
The presence of lines of weaknesses such as joints and bedding
planes will result in a faster rate of erosion.
This is because such weaknesses makes the rocks more susceptible to
the strong force of waves.
POSITION OF COAST
A coast that is exposed to strong prevailing onshore winds will be
more susceptible to erosion.
This is because it is exposed to the full force of wave action while
sheltered coast is protected.
CLIMATE
Strong prevailing onshore winds such as monsoon period will
intensify coastal erosion.
This is because wave action is much more stronger during this period.
HUMAN INTERFERNCE
Coastal defences such as seawalls and breakwaters slows down the
rate of coastal erosion.
COASTAL
TRANSPORT
COASTAL TRANSPORT
One of the ways in which waves transport sediments along a
coast is by longshore drift.
Definition: This refers to the movement of materials along a
coast by the action of waves.
Draw: Longshore Drift
LONGSHORE DRIFT
 Waves approach coast at an angle.
 Swash carries the materials up the coast at an oblique angle.
 Backwash carries the materials perpendicularly down the beach due to gravity.
 This results in a zig-zag movement of materials along a coast known as the
longshore drift.
COASTAL
DEPOSITION
WHEN?
SHELTERED COAST:
 Deposition occurs when the coast is sheltered from prevailing winds as wave
erosion is minimal in these areas.
GENTLE COASTAL SLOPE:
 On a gentle slope, depositional materials are brought by constructive waves as
swash is more powerful than backwash in this area.
WHEN?
EXCESSIVE LOAD
 During a storm, large amounts of materials are eroded from the coast. These
materials are deposited when the storm subsidies as the retreating waves are
unable to carry them.
SHALLOW WATERS
 When the coastal waters are shallow, the advancing waves break off and leave
eroded materials on the coast and deposition occurs.