What is a natural hazard?

Transcription

1 What is a natural hazard? Give me a definition not examples These words might help you A natural hazard is a naturally occurring event that might have a negative effect on people or the environment.

2 Location of volcanoes and Volcanoes and earthquakes do not occur in random locations, there are particular areas around the world with clusters or patterns of volcanoes and earthquakes earthquakes

3 The Earth s crust The crust is not all one piece but is broken into several enormous sections called plates. These plates are continuously moving and they meet at a place called plate boundaries or plate margins.

4 Exam question Describe the location of earthquakes and volcanoes (3)

5 Structure of the earth

6 The Earths Crust There are two types of crust The earth s crust consists of two different types, the crust under the oceans is a thin layer of heavy rock (basalt) this is known as the Oceanic Crust. The other is thicker and made of lighter rocks (mostly granite) this is known as the Continental Crust. Granite Basalt Together they form the Lithosphere

7 Convection currents move heat in the mantle. Heat from the interior of the earth rises to the surface. This causes the plates on the surface to move. As they cool they sink back down. Convection currents

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9 Evidence for plate tectonics? 1. Study of fossils similar fossils are found on different continents. This is evidence that these regions were once very close or joined together. 2. Pattern of rocks similar pattern of rock layers on different continents is evidence that the rocks were once close together or joined. 3. Shape of continents fit together like a jigsaw. Africa South America

10 Explain why Ice Age 4 is not accurate? -Think about theories and evidence to prove this

11 11 of 26 Boardworks Ltd 2003 A destructive plate boundary is found where a continental plate meets an oceanic plate. Destructive Plate Boundary The oceanic plate descends under the continental plate because it is denser. As the plate descends it starts to melt due to the friction caused by the movement between the plates. This melted plate is now hot, liquid rock (magma). The magma rises through the gaps in the continental plate. If it reaches the surface, the liquid rock forms a volcano.

12 12 of 26 Boardworks Ltd 2003 Name this plate boundary G A B E C F D Match the labels to the letters Earthquakes occur due to friction The oceanic crust sinks under the less dense continental crust Continental crust Oceanic plate Explosive volcanoes The oceanic crust melts and rises Mantle

13 13 of 26 Boardworks Ltd 2003 Constructive Plate Boundary At a constructive plate boundary, two plates move apart. As the two plates move apart, magma rises up to fill the gap. This causes volcanoes at this type of boundary. However, since the magma can escape easily at the surface the volcano does not erupt with much force. Earthquakes are also found at constructive boundaries. An example of a constructive boundary is the Mid-Atlantic Ridge.

14 14 of 26 Boardworks Ltd 2003 Conservative plate boundaries exist where two plates do not directly collide but slide past each other along a fault (weakness). Conservative Boundary No volcanoes are found along these plate boundaries, but earthquakes do occur. An example of such a boundary is the San Andreas Fault in California.

15 What is similar and different between each? Destructive plate boundary Constructive plate boundary Think about: volcanoes, earthquakes, direction of plate movement, ocean trench, new land formed, type of crust (oceanic or continental), famous examples Conservative plate boundary

16 Question 1 Explain how/why earthquakes occur at one type of plate boundary. You may use a diagram (6)

17 Peer marking - Question 1 Level 1 (Basic) 1-2 marks They have given a basic description of plate movement but they have not gone into much detail. For example something like Plates moving towards each other. One plate pushed below another. As plates move there are shock waves. They must have mentioned destructive / conservative / constructive boundaries Add a WWW and an EBI Level 2 (Clear) 3-4 marks They have given a clear description of the cause, and have linked statements. For example One plate pushed beneath another. As plates move, they snag and tension builds up. A sudden movement sends out shockwaves, which cause earthquakes. Level 3 (Detailed) 5-6 marks Detailed description of the cause and have linked statements together well. They have also mentioned a case study. They have also used specialist words/terms.

18 Question 2 Explain why there are earthquakes in and around Indonesia. Use this image and your own knowledge (5) Indonesia

19 Peer marking Question 2 Level 1 (Basic) 1-3 marks They have mentioned the diagram and have given the names of the plates (once only), on a plate boundary, gives a basic idea of which direction they are moving - not just plates are moving An example would be Indo-Australian plate moving towards Eurasian plate. One plate pushed below another. As plates move there are shock waves. They have not gone into much detail and their statements are not linked together. Level 2 (Clear) 4-5 marks They have linked their statements together and have explained the process in more detail An example would be Indo-Australian plate subducted beneath Eurasian plate. As plates move, they snag and tension builds up. A sudden movement sends out shock waves, which causes earthquakes in Indonesia.

20 Question 3 Explain why there are volcanic eruptions in the area highlighted on the map (5)

21 Peer marking Question 3 Level 1 (Basic) 1-3 marks They have given a basic idea of plate movement but have not added much detail, e.g. Plates are moving apart. Magma rises up from below the earth s crust. They must have stated it is a constructive plate boundary Limited evidence of sentence structure. They have spelling mistakes and poor grammar Level 2 (Clear) 4-5 marks They have given a clear explanation of why earthquakes/volcanic eruptions happen and have linked their statements together e.g. On a constructive plate boundary where plates are moving apart. As the North American and the Eurasian plates move apart, volcanic eruptions occur as magma rises from the mantle and new crust is formed. They have also mentioned the names of the plates