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
