Manly Beach is a natural feature that was created by natural processes
Manly Beach is situated on Sydney's Northern Beaches, Australia. From north to south, the three main sections are Queenscliff, North Steyne, and South Steyne.
Coastlines and beaches are shaped by the sea and the action of waves. A beach is a wave-deposited accumulation of loose sediment. Beaches are constantly changing because of processes of erosion, transportation and deposition.
Constructive Waves
- Coasts are built up and eroded by the energy of waves.
- When a wave breaks, water is washed up the beach - this is called the swash. The swash picks up sand and other material,travels up the beach in the same direction as the breaking wave.
- Then the water runs back down the beach - this is called the backwash. With a constructive wave, the swash is stronger than the backwash. Therefore constructive waves help to build up the beach.
- They are created in calm weather and are less powerful than destructive waves.
- They break on the shore and deposit material, building up beaches.
- They have a long wavelength, and are low in height.
- Sandy beaches such as Manly have a gently sloping profile or cross-section, whereas a pebble beach will have a much steeper profile. Wave action tends to shape the beach slope as well, with high-energy waves tending to increase the steepness of the slope, and lower-energy waves resulting in flatter beach profiles.
Destructive Waves
- Destructive waves are created in storm conditions.
- They are created from big, strong waves when the wind is powerful and has been blowing for a long time.
- They occur when wave energy is high and the wave has travelled over a long fetch.
- They can cause erosion of sand from beaches.
- They have a stronger backwash than swash.
- They have a short wave length and are high and steep.
Transportation and Longshore Drift
- In addition to moving material in and out of beaches waves move material along the shore.
- Waves can approach the coast at an angle because of the direction of the wind. The swash of the waves carries material up the beach at an angle. Due to gravity, the direction of the backwash and any material it is carrying tends to be in a straight line at 90°.
- The result is that material is transported along the beach in a zigzag movement.
- This movement of material is called longshore drift.
- It is usually in one direction only - that of the prevailing wind.
Deposition
When the sea loses energy, it drops the sand, rock particles and pebbles it has been carrying. This is called deposition.
Deposition occurs when:
Deposition occurs when:
- waves enter an area of shallow water.
- waves enter a sheltered area,for example a cove or bay.
- there is little wind.
- there is a good supply of material.