Coasts Kq1 Flashcards
Explain dynamic nature of coastal environments( waves, tides, currents)
Waves- Energy from the wind is transferred to the water forming waves.
-Waves shape the coast when they hit the land.
-The greater the wave energy, the greater the erosion that will take place on the coast.
Tides- Tides are the daily rise and fall in sea level.
- During periods of exceptionally high tides, waves are able to reach parts of the coast that are normally not affected by wave action.
- This can cause greater amounts of erosion to the coast.
Currents- Presence or absence of offshore currents affects deposition or erosion of sediments at coast.
Explain dynamic nature of coastal environments(geology)
Geology- Geology refers to the composition and arrangement of rocks at the coast.
- Rock composition determines the hardness of a rock and therefore how resistant a rock is to erosion and weathering. Harder rocks are more resistant than softer rocks.
- Rocks with many joints are eroded quicker than those with less joints
- The arrangement of different rocks along the coast determines the shape of coastline
Types of sediments
- Larger sediments form steeper beaches while finer sediments form gentler beaches.
Types of ecosystems
- Ecosystems are communities of plants and animals that interact with each other as well as their physical environment
- Coral reef ecosystems provide a natural barrier that slows down speed of waves on coastline
- Mangrove roots trap sediments and extend coastline further seaward and reduce coastal erosion.
Difference in constructive waves and destructive waves
1)Wave height constructive-destructive
Low-high
2)Swash and backwash constructive-destructive
Swash more powerful than backwash- backwash more powerful than swash
3)Types of breakers constructive- destructive
Swells and spilling breakers- plunging and surging breakers
4) locations constructive-destructive
Gentle coastal slope and sheltered coast- steep coastal slope and open coast
Processes of erosion( hydraulic action)
Waves striking against rock surface trap air in its joints.
This air is compressed by oncoming waves, exerting pressure on the joints.
Over time, these rocks weaken and the rocks shatter.
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 coastal cliffs.
This weakens the surface, resulting in the breaking down of the coast.
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.
Solution/corrasion
Sea water reacts chemically with water-soluble minerals in coastal rocks and dissolves them.
When solution of minerals occur, rocks are weakened and will eventually disintegrate
Describe of process(beach drift)
When waves approach coasts at an angle, they break on the shore.
The swash moves sediments up the beach face at the same angle
The 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.
Longshore current
As waves approach the shore at an angle, they generate currents in the near shore zone called a longshore current.
This longshore current moves sediments suspended in water along the coast.
Longshore drift is the movement of sediments by longshore currents and beach drift.
What are the factors that determine the amount of coastal erosion
a) types of waves
The greater the wave energy, the greater the erosion on the coast
b) Rock composition and structure.
Rocks with more lines of weakness(cracks) will be eroded more quickly.
Coasts made up of softer rocks will be eroded more quickly than those with harder rocks.
Coasts with rocks made up of minerals that are chemically reactive or can be dissolved in seawater are more easily eroded.
c)position of coast
Coasts that are more sheltered from prevailing winds experience less erosion than exposed coasts.
Headlands and bays
Headlands and bays develop on exposed coasts with alternating bands of hard and soft rocks aligned perpendicularly to the coast
Erosion of these rocks occur 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.
