Coastal environments Flashcards
Fetch
Length of time and distance over open water that the wind has blown to create a wave
Features of constructive waves
- Long wavelength
- Shallow gradient waves
- Strong swash
- Weak backwash
- Deposition of material
Features of destructive waves
- Steep gradient waves
- Tall waves with short wavelength
- Weak swash
- Strong backwash
- Erosion of material
Hydraulic action
Waves hit cliffs and force air into cracks
Abrasion
Waves pick up pebbles and hurl them against the cliff
Solution
The dissolving of soft rocks by the sea
Attrition
Pebbles carried by waves collide with each other and become smaller and more rounded over time
Deposition
Occurs when waves lose energy/material carried is too large to transport with the amount of energy the wave has
Longshore drift
- Wave swash approaches beach at an angle (the same direction as the prevailing wind)
- Backwash is at a 90-degree angle due to gravity
- Process repeats, moving sediment along the beach
- Smaller material is transported further as it requires less energy
Solution
When minerals in rocks like chalk and limestone are dissolved in seawater and carried within. The load is not visible
Suspension
Small particles such as silts and clay are in the flow of the water
Saltation
Where small pieces of shingles or large sand grains are bounced along the sea bed
Traction
Where pebbles and larger material are rolled along the sea bed
Weathering
The breaking down of rocks and other materials in situ
Mechanical weathering
Processes such as freeze-thaw, salt crystal growth, and wetting and drying of clay rich rocks
Biological weathering
When rocks are broken down by things such as plant roots, burrowing animals and nesting birds
Chemical weathering
Processes such as carbonation, oxidation and acid rain
Slumping
Waves erode the cliff base and cause instability. Rainwater permeates through the rock, saturating it, until it becomes unstable and slumps along bedding planes. Leads to a stepped appearance to the cliff
Sliding
Weathering loosens rock, which slides down off bedding planes. Leads to landslides and mudslides
Geology
Rock type e.g. granite or chalk
Lithology
Characteristics of the rock e.g. relative hardness and permeability
Discordant geology
Rock outcrops are at 90 degrees to the sea, leading to headlands and bays where there are bands of soft and hard rock interspersed within each other
Concordant geology
Rock outcrops are parallel to the sea, creating straight coastline, though it can create coves
How does vegetation influence the coast?
- Biological weathering
- Can create sand dunes via encouraging deposition, and then stabilise them
- Can protect and preserve coastal landforms by buffering and reducing wave energy e.g. mangroves