Coastal systems and landscapes
- Created by: tildamurphy
- Created on: 18-11-18 11:57
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- Coastal systems and landscapes
- systems and processes
- Types of waves
- Constructive waves - Calmer than destructive waves and are formed by distant weather systems in the middle of the ocean. They have a long wavelength and are low and surging. They have a strong swash and weak backwash, causing beach gain and gentle beach profile
- Tides
- Changes in water levels in seas and oceans caused by gravitational pull of moon and sun. Every 24hrs there is two low and two high tides
- Tidal range - difference between high and low tides
- Low tidal range - energy hits same precise area - more erosion.
- high tidal range - wave energy spread out over larger area
- Low and high energy coastlines.
- Low- constructive waves occur here, the land is low-lying
- High - destructive waves occur here, causing a lot of hydraulic action.
- Geomorpholog-ical processes
- Weathering - breakdown/disintergration of rock at/ close to ground surface. Can occur through rainfall, ice formation or action of living things such as algae/plant roots
- erosion - Erosion is a process where natural forces like water, wind, ice, and gravity wear away rocks and soil
- Transportation - the movement of material across the Earth's surface by water, wind, ice or gravity. It includes the physical processes of traction (dragging), suspension (being carried) and saltation (bouncing) and the chemical process of solution
- deposition - geological process in which sediments, soil and rocks are added to a landform or land mass. Wind, ice, water, and gravity transport previously weathered surface material, which, at the loss of enough kinetic energy in the fluid, is deposited, building up layers of sediment.
- Coastal Processes
- hydraulic action - when the motion of water against a rock surface produces mechanical weathering
- wave quarrying - Erosion that happens when high energy, tall waves hit the cliff face they have the power to enlarge joints and remove large chunks of rock in one go through vibration. This occurs due to the intense force of these waves
- abrasion - mechanical scraping of a rock surface by friction between rocks and moving particles during their transport by wind, glacier, waves, gravity, running water or erosion.
- cavitation - Air bubbles trapped in the water get compressed into small spaces like cracks in the river's banks. These bubbles eventually implode creating a small shockwave that weakens the rocks
- solution - this is when sea water dissolves certain types of rocks - such as chalk and limestone
- attrition - this is when rocks that the sea is carrying knock against each other. They break apart to become smaller and more rounded
- transportation - is the movement of material in the sea and along the coast by waves
- traction - when rocks and heavy boulders are dragged along the sea bed. This would usually occur when the waves do not have enough energy to carry the material in the water
- suspension (longshore drift) - Longshore drift happens when waves approach the beach at an angle. The swash (waves moving up the beach) carries material up and along the beach. The backwash carries material back down the beach at right angles. This is the result of gravity. Longshore drift provides a link between erosion and deposition.
- deposition - happens when the swash is stronger than the backwash and is associated with constructive waves
- sub-aerial weathering - land based processes which alter the shape of a coastline. They're a combination of both weathering and mass movement
- runoff- flow of water that occurs when excess stormwater, meltwater, or other sources flows over the Earth's surface.
- Types of waves
- Coastal landscape and development
- Cliffs - hydraulic action occurs where the waves hit the cliff face. Abrasion (once some rock has eroded away) occurs.
- Wave Cut Platforms - narrow flat area often found at the base of a cliff, created by erosion. Completely visible at low tide.
- caves - develop from widening and deepening
- arches - if two back to back caves come together, or a single cave is eroded through a headland an arch is formed.
- stacks - if the roof of the arch becomes too weak for the sides to provide sufficient support, it may collapse, leaving the seaward wall unattached from the headland and standing as an isolated pillar of rocks known as a stack.
- development of landforms and landscapes of coastal deposition
- spits - long narrow accumulations of sand with one end joined to the mainland and the other projecting out to sea.
- compound spits - when the larger sized shingle is deposited before the finer sands.
- tombolos - beach that extends outwards to join with an offshore island.
- offshore bars -
- barrier beaches and islands - series of sandy islands totally detached from but running almost parallel to the mainland.
- sand dunes -
- Estuarine mudflats/saltmarsh environments
- systems and processes
- Destructive waves - formed by local storms and are high and plunging with a short wavelength. They have a weak swash and strong backwash, causing beach loss. Beach has a steeper profile but overtime flattens
- Characteristics of Waves
- Wave fetch - the distance of open water over which a wave has passed
- Crest - the highest point of the wave
- trough - lowest point of wave
- height - distance between trough and crest
- length - distance between one crest/trough and the next
- Swash - water movement UP beach
- Backwash - water movement DOWN beach
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