2. causes of volcanoes keh


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2. causes of volcanoes keh

  1. 1. What causes earthquakes andvolcanoes?To understand the theory of platetectonicsTo be able to explain how convectioncurrents work
  2. 2. Use page 184 to label your cross section with informationand distances.Pictures to help you...piece
  3. 3. In 1912, a German scientist called Alfred Wegener proposed that SouthAmerica and Africa were once joined together and had subsequently movedapart.He believed that all the continents were once joined together as one big landmass called Pangaea and this was intact until about 200 million years ago.The idea that continents are slowly shifting their positions is called continentaldrift.What is continental drift?http://www.youtube.com/watch?v=uGcDed4xVD4
  4. 4. Study of fossilsSimilar fossils are found on different continents.This is evidence that these regions were once very close or joinedtogether.Shapes of continentsSome continents fit together like a jigsaw. AfricaSouthAmericaPattern of rocksSimilar pattern of rock layers on different continents is evidence that the rockswere once close together or joined.Evidence for continental drift
  5. 5. AfricanIndo-AustralianPlateNorthAmericanSouthAmericanEurasianPacificNazcaAntarcticPacificPlate names – the study of these plates isreferred to as plate tectonics
  6. 6. Can you name plates A and B?ABAfrican PlateIndo-Australian PlatePlate names
  7. 7. Some plates arecontinental (like theNorth American Plate)Some areoceanic (like thePacific Plate)It is at the MARGINS/BOUNDARIES ofthese plates wherethe action usuallyhappens
  8. 8. Tasks: pg 186• Draw onto your map the plate boundaries.• Put arrows onto your map to show thedirection that the plates are moving in.
  9. 9. So why do the plates move?Using only pencils, try tomove the book across twotables. Now answer thisquestion! Use page187 to help you andinclude a diagram.http://www.youtube.com/watch?v=ryrXAGY1dmE
  10. 10. • http://www.youtube.com/watch?v=ncut0iTnOgIYou canactually seethem working!
  11. 11. Structure of volcanoesTypes of volcanoHazards associated with them
  12. 12. • One in 10 people in the world live within danger range ofan active volcano.• Magma is dangerous on the surface of the earth.• There are around 1510 active volcanoes in the world.• 1510 volcanoes have erupted in the last 10,000years, which means they are active in the world ofvolcanoes.• There are thought to be many more volcanoes on the seabed.• Russia has the worlds tallest volcano at 3050m• The biggest volcano in the world is Mauna Loa in Hawaii.Its whole volume is about 80,000 cubic kilometres.• Sometimes lightning is seen in volcanic clouds. Its notclear why this happens but it could be to do with lots of hotLava
  13. 13. • This will explain why some volcanoes aretall and steep and others are wide and flat.
  14. 14. • http://www.absorblearning.com/media/item.action?quick=12s• http://www.absorblearning.com/media/item.action?quick=12yAt ……………. boundaries, when oceanic crust pushesdown underneath …………….. crust it is known as asubduction …………. Friction causes the oceanic crustto……….. The newly formed hot …………… rises up anderupts violently. The volcanoes formed here are called…………..volcanoes, meaning they are tall and ………….sided. An example of this type of volcano is………………………. in the USA.destructivecontinentalzonemelt compositesteep Mount St Helensmagma
  15. 15. • http://www.science-resources.co.uk/KS3/Chemistry/Earth_Structure/volcanoes.html• Using page 198 and 188, make your ownnotes to explain how shield volcanoesform at these margins.• KEY TERMS TO USE: shield, lessviscous, not explosive, less gastrapped, wide and gentle, movingapart, plates.
  16. 16. Quick Revision Test• You have 10 minutes to complete this test onthe sheet on your own.• I will start the time when the majority ofpeople are in the lesson and ready to go.• I will put your marks on the blog.
  17. 17. • http://education.sdsc.edu/optiputer/flash/hotSpots.htm• Draw the diagram and use the book toexplain how these are formed.
  18. 18. Name the HazardSwissEduc: Stromboli Online - Etna 1999SwissEduc: Stromboli Online – MontserratLahars
  19. 19. Lava• Lava is magma which has escaped tothe surface
  20. 20. Pyroclastic Flow/ Nuée ardentesThese are fastmoving destructiveclouds of hot gas,and ash. They cantravel up to 320km/hkm per hour. Mt Peleeproduced apyroclastic flow in1902 which killed29 000 people.
  21. 21. LaharsA mixture of water and rock flowing down the volcanoslope. A lahar looks like a mass of wet concrete that cancarry rock debris more than 10 m in diameter and moveup to 95km/h.
  22. 22. Tephra• Tephra is a general term for fragments ofvolcanic rock and lava that are blasted intothe air by explosions.It can travel thousandsof kilometers downwind from a volcano.
  23. 23. • Complete the summary sheet to show howvolcanoes can differ from each other.
  24. 24. Structure of volcanoesTypes of volcanoHazards associated with them