* High-energy waves
* Rocks that are easily eroded
1) Cliff and shore platforms
Point : A cliff is a high, steep rock face along the coast. Explanation: A cliff is formed when waves repeatedly pound against a rocky coast Elaboration: This weakens the rock, causing the lines of weakness to form in the rock face * Over time, the waves erode the coast to cut a notch along the lines of weakness. * The notch may be further eroded to form a cave
* The overhanging part of the notch or cave eventually collapses with repeated pounding of the waves, Statement: The part of the coast that is left forms a cliff Elaboration:As a cliff continues to be eroded by waves, it retreats inland. Over time, a gently
sloping or flat surface known as shore platform may develop at the base of the cliff.
Some additional details : Costal processes continue to act on the cliff and shore platform, depending on the tides. For example:
during high tide—the water extends up to the coast and covers the shore platform. Hence, waves will continue to erode the cliff at its base. during low tide-- the shore platform lies exposed above the water. Waves tend to deposit sediments onto the shore platform because its gentle slope causes the waves to lose their energy due to friction with the shallow seabed. Example : Cliff--White cliffs in Dover, Southern England
Wave-cut platform—Victoria island coast, Hong Kong
2) Headlands and Bays
Definition: A headland is a protruding area along a coast made up of more resistant rocks
A bay is an area of less resistant rocks where the coast curves inwards Point: Some coasts are made up of rocks with different resistance to erosion.
Explanation: The less resistant rocks, such as chalk erode faster, compared to the more resistant rocks like granite.
Elaboration: The different rates of erosion of the rocks along the coast produce the uneven coastline. (A coastline is the general appearance of the coast, as seen from the sea.) Elaboration: The less resistant areas of rocks curve inwards as they get eroded away by the waves, forming bays. The areas made up of more resistant rocks will protrude out from coastline. These areas are known as headlands. Example:southwest coasts of Wellington in the South Island of New Zealand Extra information: Due to the wave refraction,
* wave energy is concentrated on the headlands and
* wave energy is weakened along the wider stretches in the bays. Thus, materials are deposited along the shores of bays.
Page 145—wave refraction
Definition: bending of waves as a result of differences in wave speeds Due to wave refraction,
* Wave energy is concentrated on the headlands
* Weakened along the wider stretches in the bay.—(thus materials are deposited along the shore of bays)
Landforms by transportation and deposition (deposition is the main process) * Low-energy waves
* Longshore currents
Point: A beach is an accumulation of sediments on the coast. Explanation:Beaches form when waves, tides or currents bring and deposit materials onto the shore.
* In fact, different types of beaches, comprising different types of materials can be found along the coast, producing beaches with different gradient.
A beach made of coarser materials like small rocks, gravel and shingle, is generally steeper than one made up of less coarse materials like sand because when the coarser materials are deposited by the swash, the backwash can hardly remove them.
* Beaches are constantly changing as their shapes and sizes are affected daily by waves, tides and currents. For example, during calm weather, constructive waves can help to deposit materials on the beach and build it up further. On the other hand, during coastal storms, strong waves will remove materials from the beach, eroding it....