Coastal Landscapes Year 8 Geography Learning Intention Identify

Coastal Landscapes Year 8 Geography

Learning Intention Identify characteristics and landforms found in coastal landforms. Identify causes, impacts and responses to a geomorphic hazard.

What are Coastal Landscapes? Read text page 96.

What forces shape coastal landscapes Read page 97 -98 of text. Coastlines are dynamic environments, undergoing constant change. Coastal landforms can be divided into two major categories: Erosional Depositional

Erosional Coasts Read pages 102 -103 of your text. Erosional coasts are formed by the powerful action of waves and other forces that weather and erode rock. Erosion is the transporting of materials that has been weathered (worn away) from one place to another. There are two types of erosion: Wind Water The Victorian and South Australian Coastlines are mostly erosional.

Erosional Landforms The type of waves that erode and destroy sections of coast are known as destructive waves. Destructive waves are tall and frequent that crash into the shoreline, digging out large chunks of land. Destructive waves originate from stormy large oceans.

Activity 1 Construct a photo sketch of Source 3. 10 on pages 102 -103 in your books. Annotate (label) your sketch. Make sure you include: Cliff Cave Gorge Arch Headland Bay Stack EXT: Write a brief definition or description about each coastal landform element on your sketch.

Activity 2 1. Why do some rocks erode more than others? 2. Study Source 3. 10 a. How many caves, arches, and stacks can you identify? b. Describe the waves in this landscape. What evidence is there that they are destructive waves?

Depositional Coasts Read pages 104 -105 of your text. Depositional coasts are made up of eroded materials transported/deposited along the coast. Depositional coasts are those dominated by beaches and sand dunes. The Qld and northern Western Australian Coastlines are mostly depositional.

Depositional Landforms Unlike destructive waves, constructive waves have characteristics that allow plants and animals to live and thrive. Constructive waves are long and slow and begin far out to sea and gently roll onto the shore, slowing for a smooth and gentle landing. A beach is a common depositional landform and as it piles more and more sand other materials onto the beach, together with the wind, it forms sand dunes.

Activity 3 Find a real life image of a depositional coastline. Annotate the diagram with the names of coastal landform features.

How are waves formed Waves are formed in the ocean and may originate thousands of kilometers away from the beach. Waves are created by the transfer of energy from winds blowing across the ocean surface. Wave begins at sea with wind across surface water Water surface rises with wind and pulled back down by gravity Tug of war between drag of wind and pull of gravity creates an orbit beneath the surface Wave moves into shallow water and bottom of orbit hits the sea bed. Friction slows the bottom of wave more than top Top (crest) continues and finally falls onto the shore

The power of waves The water that falls forward and moves up the beach is the swash. The backwash is the water that runs back to the ocean.

Destructive waves When waves are large and steep the backwash becomes more powerful. These waves remove sand other material from the beach and are called destructive waves. They cause erosion of the beach.

Constructive Wave When a low energy wave crashes on a beach, it has less backwash and most of its sediment is dropped during the swash, so it becomes a constructive wave. They build up a beach.

Activity 4 1. Describe the movement of a destructive wave compared to a constructive wave. 2. How do waves change the coast? 3. What do you think happens to sand on a beach where waves strike directly onto the beach rather than on an angle?

Longshore Drift Read pages 100 -101 of your textbook.

What is it? Most waves hit the coast at an angle. When the waves hit the coast at an angle, the swash carries it along the beach rather than just dumping it directly forward onto the shore. The next wave that comes along will also move the sand along the beach until eventually, after hundreds of small zigzags, many grains of sand are moved to one end of the beach.

Activity 5 1. Why is longshore drift considered a major contributor to the shape of the coastline? 2. What problems are associated with longshore drift? 3. Study the diagram showing the process of longshore drift. What is the direction of the: (a) waves (b) wind (c) swash (d) backwash (e) longshore drift? 4. Predict what will happen to a beach if longshore drift occurs mostly in one direction. 5. Study the diagram showing seasonal longshore drift at Hampton Beach. a. What is the direction of longshore drift in summer and in winter? b. Describe what happens to the sand in each case. c. What has been the impact of the breakwater on Sandringham Harbour? d. Predict what might happen if the breakwater or groynes were removed. Show this in a diagram.

Sand Dunes As the tide goes out, the sand dries out and the wind can then pick up individual gains and blow them inland. As the grains move, they may be trapped by an obstruction, such as plants, or they may collect in areas sheltered from the wind. As the sand piles higher it forms sand dunes. Plants grow on these dunes and hold them together.

Blowout Dunes If the plants are removed, entire dunes can gradually move further inland, covering roads, car parks, paddocks and plants. These are called blowout dunes.

Spit A spit is a long, curved landform that is built up at the mouth of the river. The river carries soil and rocks upstream and is dumped at the river mouth forming the spit. Over time ore soil and rocks collect making it more secure. As it stabilizes plants grow and a habitat forms.

Lagoon Some spits grow so large the river may change it course in order to reach the sea. Over time the river mouth may move hundreds of metres along the coast and a stretch of calm water behind the spit is formed called a lagoon. They are often home to plants and birds.

Tombolo A tombolo is formed when waves curve around an island close to shore and deposit a bar of sand or other sediment close to the mainland. Eventually enough materials build up to create a permanent connection – a tombolo- between the island mainland.

Activity 6 Locate in Queensland examples of: Sand dune Blowout dune Spit Lagoon Tombolo Sketch and annotate each example.

Activity 7 1. Why do constructive waves tend to add sand to a beach rather than take it away? 2. What role does the wind play in the formation of sand dunes? 3. Why are is important to maintain sand dunes? 4. Why are waves important to the formation of a tombolo? 5. Draw a sketch map of Whitehaven Beach showing the locations of sand, sea, rivers and forest.