Coasts KQ1 Flashcards
Describe the coastal erosion process of hydraulic action
Waves striking against a rock surface trapping air in its joints.
This air is compressed by the oncoming waves, exerting
pressure on the joints. Over time, these joints weaken and the rocks shatter.
Describe the coastal erosion process of abrasion/corrasion.
As waves break, sediments carried by waves such as sand and rocks are hurled against the coast. These loosened sediments knock and scrape against the coastal cliffs. This weakens the surface, resulting in the breaking down of the
coast.
Describe the costal erosion process of attrition.
When rock particles carried by waves rub or hit against one
another, they break down into smaller pieces and become
smoother and more rounded over time.
Describe the coastal erosion process of solution/corrosion
Sea water reacts chemically with water-soluble minerals in
coastal rocks and dissolves them. When solution of minerals occurs, rocks are weakened and will eventually disintegrate For example, limestone rocks are easily eroded by carbonic acid
in solution.
Describe the process of longshore drift
Waves approaching the shore at an angle break on the shore. The swash moves sediments up the beach face at the same angle. Backwash moves sediments perpendicularly down the beach face. This process repeats as waves hit the beach. Beach drift is the zigzag movement of sediments along the beach. As waves approach the shore at an angle, they generate currents in the near shore zone called a longshore current. This longshore current moves sediment suspended in the water along the coast. Longshore drift is the movement of sediments by longshore currents and beach drift.
How do headlands and bays form?
Headlands and bays develop on exposed coasts with alternating bands of hard and soft rock aligned perpendicular to the coast. Erosion of these rocks occurs at different rates causing the rocks to erode unevenly. The softer rocks erode faster forming indents in the coastline called bays, while the more resistant rocks protrude out to sea as headlands.
Explain why erosion is greater on the headlands than in the bays.
As waves approach an indented coastline, they reach the water off the headlands first and slow down. The wave front curves to become more parallel to the coast. Thus, when the waves converge on the headlands, the height of the waves increase which increases erosive energy. When the waves diverge in the bays, the height of the waves decreases which lowers erosive energy.
How does a shore platform form on a sea cliff?
Waves attack a steep slope through hydraulic action and abrasion forming a notch along a line of weakness. Prolonged erosion of the notch causes it to enlarge to form a cave. Further erosion causes the cave to collapse, and a steep cliff is formed. As the process of cliff formation continues, the cliff retreats landward, and thus, a shore platform forms in front of the cliff.
How does a stack form from a headland?
Waves attacking lines of weaknesses in a headland may form a notch through erosional processes such as hydraulic action and abrasion. Continual erosion enlarges the notch to form a cave. The cave enlarges and deepens and an arch is formed when the cave cuts through the headland. The sides of the arch continue to get eroded until the weight of the arch causes it to collapse. This leaves a pillar of rock separated from the headland called a stack.
How is a spit formed?
A spit is formed by longshore drift. Since longshore drift does not change direction even when the coastline bends suddenly, material will continue to be transported in the original direction for a distance and is deposited into the sea. Over time the deposited material will rise above the water, thus forming a spit.
How is a tombolo formed?
A tombolo is formed when a spit joins a nearby island.
