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• A coast is a zone where the land meets and interacts with the sea.
• The coastal environment is the result of interactions between the land (lithosphere), water (hydrosphere0 and living things (biosphere). Coasts are always changing
• Offshore: the submerged zone below the low tide shoreline

  Foreshore: between the low tide and high time shorelines

  Backshore: stretched landward from the highide shorline to the hgihest water line
• Coastal environments vary from place to place. The variations depend on how much they are affected by natural processes and human activities
• the constant influence of natural processes and human activities means that coastal environments are ever changing and dynamic
• Wave action is the main shaping force of the coastal environment. It is a rising and falling movement of the water surface. It is generated by winds blowing across the sea or oceans. Energy from the wind is transferred to the water and it is tis wind energy that helps shape coasts when the waves hit land.
• Tides refer to the daily alternate rise and fall in the sea levels.

  It is caused mainly by the effects of gravitational pull of the moon and sun on the earth.

  it affects processes such as coastal erosion, sediment transportation, and sediment deposition.

  During high tides, the foreshore is affected by wave erosion
• Currents are large scale, continuous movements of water in seas or oceans.

  They are produced by a combination of winds, the Coriolis effect, water density and temperature differences.
• Geology refers to the arrangement and composition of rocks.

  • Well jointed rocks offers more lines of weaknesses to erosional processes.
  • rock composition determines the hardness of rocks and their resistance to erosion, affecting the rate of change along coasts.
• Coastlines refer to the outline/ contour of a coast
• reasons for dynamic coastal environments:

  • waves
  • tides and sea level changes
  • ocean currents
  • geology
  • types of ecosystem
  • human activities
• waves form when winds blow over the surface of the ocean. The friction from the wind causes the water particles near the surface to move in an orbit, creating waves
• wave trough:

  • lowest point of the wave

  wave crest:

  • highest point of the wave

  wave height:

  • distance from crest to trough

  wave length:

  • distance from crest to crest or trough to trough

  wave steepness:

  • ratio of wave height to wave length

  wave frequency:

  • number of waves that reaches a particular point within a time period (the higher the wave frequency, the more destructive the waves are)

  wave period:

  • time taken fro the waves to travel through one wavelength
• What happens as waves approach the shore?

  1. The seabed interrupts the orbital movement of the water
  2. As the seabed becomes shallower, the orbit becomes more elliptical
  3. This causes the crest of the aves to rise up and eventually topple on the beach
  4. The water that rushes up the beach is called the swash
  5. The water that flows back towards the sea is called the backwash
• How do waves break?

  1. When waves approach the shore, teh water depth decreases and the wave will start feeling the bottom
  2. Friction reduces wave velocity
  3. As the waves feel the bottom, the orbital movement of water changes to elliptical shapes
  4. As the wavelength shortens, teh wave height increases
  5. Eventually, the steep front portion of the wave cannot support the water as the rear part moves over, and the waves break
  6. The swash will rush up the beach
  7. The backwash will flow back towards the sea
• Factors affecting wave energy:

  1. wind speed - the greater the wind speed, the greater the wave energy
  2. wind duration - the longer the wind blows, the more energy the waves have
  3. length of fetch - the greater the fetch, the more energy the waves have
• Constructive waves:

  • gentle beach gradient
  • low wave height
  • long wave length
  • low wave frequency
  • high wave period
  • swash > backwash
  • low energy waves
  • prominent deposition process
• destructive waves:

  • steep breach gradient
  • high wave height
  • short wavelength
  • high wave frequency
  • low wave period
  • backwash > swash
  • high energy waves
  • prominent erosion process
• 4 types of erosion:

  1. hydraulic action
  2. abrasion
  3. attrition
  4. solution
• hydraulic action:

  Waves break against a rock surface by their sheer weight and power. Air is also trapped in the cracks in the rocks. This air is compressed by the oncoming waves, exerting pressure on the cracks. Thus, the rocks will weaken and eventually break apart
• abrasion (/corration)

  As waves break, sediments carried by waves will hurl against the coast. These sediments knock and scrape against the coastal cliffs, weakening the surface and breaks down the coast. Overtime, the impact is powerful enough to undercut a cliff.
• attrition:

  rock particles carried by waves rub/hit against one another, chipping and grinding the particles down into smaller, smoother, rounder and finer pieces.
• solution (/corrosion):

  Sea water reacts chemically with water-soluble minerals in coastal areas and dissolves them. When solution of minerals occur, rocks are weakened and eventually disintegrate
• longshore drift:

  The longshore current flows parallel to the coast, and is generated by winds, tides and waves approaching at an angle.

  • the swash carries materials up the coast at an angle
  • the backwash carries materials back to the sea at 90 degree angles due to the pull of gravity
  • this results in a zig zig movement of sediments along the coast
• deposition:

  occurs when small/low energy waves do not have the energy to carry the load, resulting in sediments laid down along the coast.

  • larger sediments are deposited first, followed by smaller sediments
  • as the distance from the shoreline increases, the size of sediments being deposited increases
• Cliffs and wave cut platforms

  1. High energy waves approach the coast. The impact of the water hitting against the coast erodes the coast along lines of weaknesses. Other erosional processes can also attack the coast simultaneously. Overtime, a notch forms.
  2. Continuous erosion of the notch causes it to enlarge, forming a cave.
  3. As erosion continues, the cave becomes deeper and larger, resulting in an overhang. The roof of the cave eventually loses support and collapses. The cliff, forming a new cliff face.
  4. As the cliff retreats, it leaves behind a gentle platform called a wave cut platform.
• Headlands and bays:

  1. waves approach a discordant coastline made up of alternating layers of resistant and soft rocks. More resistant rocks are eroded at a slower rate than softer weaker rocks
  2. Overtime, differential erosion results in an irregular coastline, where the more resistant rocks juts out into the sea, which the softer rocks form an indented coastline
  3. The indented coastline forms a bay and the part of the coast that juts out into the sea forms the headland
• Caves, arch, stack, stump:

  1. Wave energy is concentrated at the headland when wave refraction occurs, causing it to erode and create notches.
  2. Notches enlarge and deepen as waves continue to erode, forming caves. Continuous erosion deepens the caves, until they eventually meet and cut through each other, resulting in an arch.
  3. The arch weakens as waves continues to erode it. Overtime, the roof of the arch collapses.
  4. A column of rock separated from the cliff is left behind, forming a stack.
  5. The stack further erodes and weathers. reducing to form a stump, which is only visible during low tides.
• Beaches:

  A beach is a zone of sediment deposition formed from loose sand, gravel, pebbles, broken shells and corals. They are formed when waves, tides or currents bring deposit material onto the shore. A beach is constantly changing as their shapes are affected daily by waves, tides or currents.

  • a beach made up of coarse materials are steeper than one made up of less coarse materials.
• Spit and tombolo:

  1. Longshore drift carries materials along the coast, even if the coast changes direction, so, sediments continue to be transported and deposited.
  2. Overtime, accumulation of deposits rises above sea level, forming a narrow ridge of sand with one end attached to the coast. This is called a spit.
  3. Wave refraction may cause the free end of the spit to curve inward, forming a hooked spit.
  4. As longshore drift continues to extend the spit, it may join to a nearby island, forming a tombolo