2. Defining the Coastal Area / Zone
• The coastline is the line where the land and sea
meet.
• The coast is a zone or strip of land extending from
the coastline, which borders the sea to where the
land rises inland. Its limit is marked by the level of
high tide.
• The shore is the zone which lies between mean
high low water mark and high water mark and
constitutes both the backshore and foreshore.
• Backshore is the zone between mean high tide
level and the coastline.
• Foreshore is the lower zone of the beach lying
between the low and high water level.
4. Features Produced by Wave or
Marine Erosion
• Cliffs
• Headlands and bays
• Waves, arches and stacks
• Wave-cut platforms
• Blow Holes or Gloups and Goes
5. Cliffs
Most fundamental and ubiquitous feature of rock
coastlines. Variations based on differences in
• Lithology
• Jointing
• Structure
• Degree of exposure
• Erosional History
• The dip of the rock
• Wave action
• Sub-aerial erosion
6. Dead or a(Live)
• Classification into Live or Active cliffs,
those which are experiencing wave
erosion , or experiencing sub aerial
activity, gullying, soil creep or slumping.
They often have free-faces
• Dead cliffs are isolated from the sea by
sand, shingle, sand-marsh deposits, and
rock marsh
7. Cliff Development
1. Removal of a wedge-shaped mass of rock, ( a
notch) largely by the mechanical action of
breaking waves, often utilizing some weakness
2. Once this has been initiated, basal attack,
weathering and slumping, gullying and mass-
movement wear down the headland
3. The cliff increases in height and the wave-cut
platform is extended
8. Cliff Development
• 4 As the wave cut platform develops, the
process slows down as the shallower
water over the platform slows down, and
the basal attack is less intense.
9. Headland and Bays
• Where there are alternating beds of hard and
soft rocks, the hard rocks offer a greater
resistant to erosion . They eventually stands out
as headlands, that is, as promontories with
steep cliff sides projecting out into sea.
• The softer rocks are easily eroded as they are
less resistant to marine erosion. In due course
an indentation or cure in the land, called a bay is
formed. Bays are separated by headlands.
12. Processes
• Several other processes are found in and
on cliffs, these include
• Sub-aerial processes ( Weathering and
Mass movement); e.g. slumping, sliding,
soil-creep, freeze-thaw, carbonation, salt-
crystallization, biological weathering
13. Rates of Cliff Recession
• Variation based on the
• Structure of the rock
• The Aspect
• The vegetation
• Man’s impact
• Protect ional features
14. Notches
• These are grooves that are eroded into cliffs
• Between mean high tide and low tide
• Extremely important in cliff development
• Develop in areas of weakness
• Variations include smooth rounded rocks in
limestone and chalk ( chemical action)
15.
16. Wave Cut Platforms
Tremendous variation
• Some are temporary, some permanent.
• Some are covered with sand and shingle, others
have channels, trenches and hollows
• In hard rock the platforms are poorly developed
whereas in soft homogenous rock there are
broad, even surfaces with minor furrows
17. Wave-cut platforms
• Formed by wave abrasion, and solution
• Delicate balance based on the resistance
of the rock
• Weak rock will collapse
• Strong rock resistance will be minimal
20. Caves, arches and stacks
• Caves – a natural underground hollow formed by
erosion’
• Arches – formed by the wearing away of narrow
headland, generally by the formation of two back-to
back caves which eventually join. These are temporary
and eventually collapse
• Stacks- Tall isolated pillars of rock that are free standing
in the sea, alone or in a group. They may result from the
collapse of an arch and are normally residual features
formed from a former headland
• Stumps rocky platforms offshore that may be covered at
high tide, but may be uncovered throughout the day.
25. Geos
• Long, narrow gorge-like inlets, normally
formed because of the collapse of a cave
26.
27.
28.
29. Features Produced by Marine
Deposition
• Beaches
• Spits and Bars
• Tombolos
• Mudflats
• Sand Dunes
30. Beaches
• A beach is an accumulation of materials
such as boulders, pebbles, shingle, sand
and mud on a sloping or shelving ground.
The waves which break offshore result in
its erosive power decreasing . This is
caused by the swash and backwash which
deposits materials on the shore.
32. WHAT ARE SPITS?
Spits are generally linear deposits of
beach material attached at one end to
land and free at the other. Where the
direction of the coast changes, sediment
carried by longshore drift may form a
tongue of sand and other material, which
is called a spit
33. HOW ARE SPITS FORMED?
.
Spits are formed when a large accumulation of
material forms a narrow strip of land that juts out
into the sea but is still connected to the
mainland.Where a river carries large amounts of
material into a bay, waves moving obliquely will
transport the material in a diagonal direction
along the beach by the process of longshore drift.
An example of a spit is the Cocal spit at the
mouth of the Nariva River on the east coast of
Trinidad
34. CONDITIONS NECESSARY TO
FORM A SPIT
• There must be a good supply of sand and other
sediments
• Waves must approach the coast at an angle, so
that longshore drift moves material along the
coast
• The sea must be relatively shallow
• The sea is usually fairly calm, with low-energy
constructive waves
35. WHAT ARE TOMBOLOS?
A linear deposit of sand or stones,
formed by longshore drift, which joins
an island to the mainland is called a
tombolo.
An example of a tombolo is the
Palisadoes in Jamaica
38. MUDFLATS
• Mudflats are lowlying parts of the coast which
are submerged at high tide and low tide. They
are normally located behind a bar or sandpit or
besides estuaries and are comprised of silt or
clay. In tropical areas mudflats support dense
tropical mangrove vegetation community often
with large area of swamp.
40. SAND DUNES
• Some sea shores consist of ridges of sand
deposits by waves and shaped by wind. These
are termed sand dunes. They are confined to
coastal areas which are lowlying and are above
sea high water tidal level.
• The onshore winds blowing across sandy
beaches constantly renew and shape the sand
deposits. Vegetation on the coast trap the sand
and causes it to be stationary .
• Sand dunes are common in Port Royal in
Jamaica and Sandy Belt in Guyana.
