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Shaping Coastal Landscapes
Transcript of Shaping Coastal Landscapes
Cyclones, extreme waves and storm surges with enhanced power
Rise in surface temperatures and mortality Future Predictions Strategies For Prevention Buildings, roads and tourist developments located further away from coastline
Keep waterways free of rubbish
Coastal ecology education Coolum Boardwalk Noosa Main Beach “The erosion carved out small 'cliffs' in the sand dunes, which nesting female turtles are unable to climb.” - Jackson Vernon A real world issue So what leads our coastal landscapes to change? Weathering A slow process that breaks down rocks into smaller pieces.
There are different types of weathering..... Causes of Weathering Wind Rain Flowing Water Physical Weathering Waves crashing cliff breaks off pieces of land Rainfall freezes and widens cracks Flowing water smooths out rocks Plant roots crack rock Chemical
Weathering Water and carbon dioxide creates limestone caves Water and oxygen cause the rusting of iron chains Weathering makes rocks and other land weaker. Erosion is the movement of solids away from one place to another. Large changes in temperature can cause expansion and contraction of rocks.
During the day, the outer surfaces of rocks expands, while the centers of the rock remain cool.
At night, the surface layers of rocks cool and contract.
The constant expansion and contraction weakens the surface layers of rocks. Eventually, the weakened surface layers "peel" off or break into small pieces Temperature As plants grow, the roots force the cracks to widen and eventually pry the rocks apart. Plants? Not only do our cliffs change shape, so do our beaches. Parts of a Wave Constructive
(swash is stronger than backwash - builds up coast) Wave Action Destructive
(swash is weaker than backwash - erodes coast) 4 main ways coastline is eroded:
-CORROSION (materials are dissolved by acidic seawater)
-CORRASION OR ABRASION (sediment wears down rocks and makes them smooth)
-ATTRITION (rocks hit each other and break up)
-HYDRAULIC ACTION (constant pressure of the water against the shore/cliff) Coastal Erosion http://www.wiley.com/college/strahler/0471480533/animations/ch19_animations/animation2.html Wave Refraction waves slow down in shallow water, bending and eroding headlands Hydraulic action at the water line of a cliff is called undercutting.
Undercutting causes cliffs to become steeper because they are unable to support themselves and pieces break off. Undercutting Caves
Wave-Cut Platforms What Does Undercutting
Cause? Longshore Drift the movement of sand and sediment along a beach caused by waves and currents a form of deposition Depositional Features Spit - a ridge of sand created by longshore drift
Tombolo - a spit that has grown to connect an island to another island
Groynes - man-made barriers built to stop sand from being removed from a beach by longshore drift Estuaries: bodies of water that rise and fall with the tides Estuary By the year 2030, it is estimated that 21 million people are likely to live
near the Australian coast. Some of the landforms resulting from erosion are cliffs, rock
platforms, headlands, caves, blowholes, stacks and arches. In places sheltered from strong winds and waves, sediments are deposited to form features such as beaches, spits, dunes, estuaries and lagoons. Landforms produced by erosion make
up 27 per cent of Australia' s coastlands and include
cliffs, arches, caves and blowholes. Landforms produced by deposition (constructive waves) make up 73% of the coast and include:
-alluvial plains and swamps (41%)
-beaches, dunes, tombolos, spits and bars (24%)
-estuaries, lakes and lagoons (8%). When the weather is very windy and waves are large, the coast can erode rocks and move sediment.
Such waves are called destructive waves.
Some coastal rocks are harder than others and resist erosion; other rocks are softer and erode more easily. Constructive waves are smaller and contain less energy — they carry sand or other material up the beach in the swash and deposit it there. (Beaches are formed by constructive waves.)
Destructive waves carry more material to deep water in the backwash. The largest waves are produced by strong winds
blowing in a constant direction for a long time over a wide expanse of ocean. The base of the wave is slowed down by friction against the seabed while the top of the wave keeps going at the original speed. The
wave becomes higher and then breaks. -Waves usually approach at an angle that depends on the direction of the wind.
-The result is that material is transported
along the beach in a zigzag movement.
-You may have experienced this when you have ended up some distance along the beach from where you left
-This movement of material is called longshore drift and is usually in one direction only that of the wind. Landforms Tides are due to the gravitational force of the moon
and the sun acting on the rotating Earth.
Tides can move a lot of sediment into and out of bays and estuaries. Rips also move sediment. Rips are localised, fastflowing
currents that run out towards the sea.
Rip currents depend on the height and duration of
the waves and on the contours and shapes of the
seabed. Sand dunes are formed by the wind when dry sand is blown to the back of the beach and trapped.
The initial dune is called the fore dune.
Back dunes may develop behind the fore dune. Grass usually traps the sand.
Over time other plants, such as shrubs and trees, will grow helping to stabilise the back dunes. 1 What are the two main coastal processes that form coastal landforms?
2 Describe the type of weather and waves that erode coasts.
3 Explain how waves can both build and destroy
coastlines. Review A storm surge is a rise in sea level resulting from intense storm.
Cyclone winds whip up the ocean surface, and low pressure systems can put less pressure, or weight, on the sea allowing the surface of the sea to actually rise.
(Think of what happens when you drop something in water) 1. Define the terms wave climate, swash, backwash, longshore drift, rip, tide and storm surge.
2 Explain the ocean processes that affect the east coast of Australia.
3 Explain how sand moves along a beach. Soft rocks are eroded more quickly by wave erosion than harder rocks.
Headlands and bays form along coasts that have alternating resistant (harder) and less resistant (softer) rock.
Where there is resistant rock, the coast is worn away more slowly leaving a headland that juts out into the sea.
Where there is softer rock, wave erosion is more rapid and a bay will form. Headlands and Bays Wave energy is concentrated around headlands, which are eroded forming landforms such as cliffs, rock platforms, caves, arches, stacks and blowholes. The impact of waves at the foot of a cliff forms a wave-cut notch.
Wave erosion enlarges the notch, the cliff is undercut and eventually the cliff collapses.
As this process is repeated the cliff slowly goes inland. Headlands and cliffs often contain weak areas
such as faults or softer rock. Sea caves are formed
because weaker areas are the first to be worn away. If sea caves form on both sides of a headland, or if the waves erode through the sea cave to the other side, an arch or bridge is formed.
Further erosion of the rock supporting the arch may then cause it to collapse, leaving a stack. When water rushes into a sea cave, it can cause
pressure to build at the back of the cave.
If a section of rock in the roof of the cave is weak, part of the roof may collapse and a blowhole is formed. 1. How are the following landforms formed?
2. What are the 4 types of coastal erosion?
3. What role do strong waves have on coastal landforms? Now watch the video from the beginning of the Prezi again.
Identify the coastal landscapes. What processes shaped the 12 Apostles?
What stages would it have gone through? If not working, open up video file in Coastal Landscapes Folder. Coastal Erosion Coastal Deposition So how are all these landscapes formed? Broadbeach after storm surge. Taken 10/02/2013. 3 MAJOR PROCESSES SHAPE OUR COASTLINES: