coastal landscapes Flashcards
what are the characteristics of destructive waves
- Large steep wave plunges over
- Beach cliff forms
- Strong backwash
- Weak smash
- Little percolation through sand
- Eroded material deposited
offshore in longshore bars
what are the characteristics of constructive waves
- Strong swash transports sand up the beach to for a berm
- Low flat waves spill over
- Orbital motion of wave becomes more elliptical with sea bed contact
- Material from offshore bars moved onshore
- Weak backwash much percolation through sand, little transport of sand down the beach
Why is the process of refraction important?
Why is the process of refraction important?
* At a discordant headline, as waves hit the headland they converge and erode the sides of the headlands. As the waves lose energy, they undergo deposition at the bay which leads to the formation of a beach as sediment accumulates.
* At a discordant coastline (alternating bangs of less and more resistant rock) waves converge around the headland as wave refraction occurs (2)
* Waves concentrate their energy around the headland, leading to high levels of erosion and therefore erosional landforms are created (1)
* Wave energy is therefore dispersed and low energy waves reach the bay leading to more deposition and the creation of more beaches (1)
what is a neap tide
when the moon and the run are at 90 degrees in relation to the earth
what is spring tide
when the moon, earth and sun are in line
define thermohaline
Thermohaline = the circulation of ocean water of different densities due to their temperature and salt content.
what are the characteristics of a high energy coastline
Waves are powerful
The rate of erosion exceeds the rate of deposition
Characteristics such as cliffs and wave cut platforms
what are the characteristics of a low energy coastline
Waves are not powerful
The rate of deposition exceeds the rate of erosion
Characteristic landforms include beaches and spits
what is the littoral zone
The littoral zone is the near shore area where sub light penetrates sediments, allowing for aquatic life to flourish, but faces rapid change continually.
how often do spring/neap tides occur
twice in a lunar month
what is a sediment cell
Sediment cells are distinct areas of coastline separated from other areas by well-defined boundaries, such as headlands and stretches of deep water. Their inputs and outputs of sediment are balanced within each cell. Sediment cells vary in size.
what is the definition of weathering
Coastal weathering is the disintegration of rock as it loses its integrity or coherence. The rock mass stays largely the same, but its structure is increasingly fragmented
what are the different types of weathering
chemical
mechanical
biological
what is freeze-thaw weathering
Primarily occurs in temperature humid climates. Water enters cracks in rocks, freezes and expands by 9%. This causes the rock to crack and pieces to fall off
what is onion skin weathering
Usually occurs in arid reasons. Temperature rises, rocks heat. As the rock heats, it expands. At nigh as temperature falls, the rock cools and contracts. This causes the outside layer of the rock to peel away.
what is wetting and drying
Coasts are often rich in clay; these clay-rich soils will expand when they are wet and contract when they are dry. This process of expanding and contracting cracks the rocks, making them vulnerable to freeze-thaw and salt crystallisation.
salt crystalisation
Occurs in semi-arid conditions. Water evaporates from rocks, leaving behind salt. This causes a dramatic increase in volume, leading to the rock cracking and pieces falling off.
what is carbonation
Coastlines composed of chalk or limestone may be dissolved by acidic rainwater or seawater. The rain/sea absorbs co2 from the atmosphere, creating a weak carbonic acid.
This can convert solid calcium carbonate to soluble calcium bicarbonate and the rock dissolves.
what is oxidation
Rocks containing iron compounds experience oxidation of the iron into a ferric state (rusting) when oxygen and water are readily available from air or sea. This can lead to disintegration.
what are the different types of erosion
hydraulic action
abrasion
solution
quarrying
attrition
what is the process of hydraulic action
The waves force air into the cracks in rocks causing it to break
what is the process of abrasion
Rock fragments being thrown onto the cliff face, weakening the cliff structure
what is the process of quarrying
The waves scoop loose rocks out from the cracks formed in rocks
what is the process of solution
Chalk and limestone is dissolved and rock is removed in solution
what are the different types of transportation
traction
saltation
suspension
solution
what is traction
Large particles like boulders are pushed along the sea bed by the force of the water
what is suspension
Small particles like silt and clay are carrying along in the water
what is saltation
Pebble sized particles are bounced along the sea bed by the force of the water
what is solution
Soluble materials dissolve in water and are carried along
what is soil creep
The slow movement downhill of individual particles due to gravity. Raindrops may dislodge particles, which will slowly move downhill due to gravity
nature of movement: slope
rate: slow
wet/dry: wet
what is mudflow
Heavy rain can cause large quantities of fine material to flow downhill. As surface layers become saturated, water carries mud downhill.
Nature of movement: slope
rate: fast
wet/dry: wet
what is a landslide
Occur on cliffs made from softer rocks or deposited material, which slip as a result of failure within it when lubricated, usually following heavy rainfall
nature of movement: diagonal
rate: fast
wet/dry: wet
what is slumping
Where softer material overlies much more resistant materials, cliffs are subject to slumping. If lubricated, whole sections of the cliff can move downwards
nature of movement: rotational
rate: slow
wet/dry: wet
what is rockfall
These occur from cliffs undercut by the sea, or on slopes effected by mechanical weathering like frost action
nature of movement: vertical
rate: fast
wet/dry: dry
what is solifluction
Mass movement of soil and Regolith affected by alternate Freezing and Thawing. Characteristic of Saturated soils in high latitudes, both within and beyond the permafrost zone.
what is regolith
the layer of unconsolidated solid material covering the bedrock
what factors effect coastal landscapes on a spatial and temporal scale
Climate
Temperature range
- Freeze thaw especially in places with large diurnal ranges
- Onion skin weathering
- Melting of ice, more sediment
Wet climates
- Weathering - carbonation from acid rain
- More mass movement (slumping landslide)
- Wetting and drying
Tides/waves
Wave steepness
- More plunging waves remove more sediment
- More spilling waves, deposit more sediment
Length of fetch
- Higher energy waves (more destructive waves)
Gradient of sea bed
- Sudden change in gradients make more destructive waves
Humans
Construction of groynes
- Blocks longshore drift, leads to the rest of the sediment cell will be starved from their sediment sources
Dredging
- More dredging decreases fluvial sediment
what structural factors effect the coastal landscape
dip of cliff
strata
rock resistance
rock type (carbonation/oxidation)
precipitation
vegetation
human interference
tidal range
low/high energy coastline
