Earthquakes

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Leaving Certificate slides on Earthquakes - causes, areas, features, measurement, effects, case studies

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Earthquakes

  1. 1. 3 Key Terms FOCUS – starting point of earthquake, deep underground EPICENTRE – Point on surface, directly above focus. Earthquake is strongest here FAULT – Dividing line between 2 plates
  2. 2. 2013 HL
  3. 3. Earthquake Depths Shallow – 70K or less below ground. Contact between Continental Plates. MOST DESTRUCTIVE. Intermediate – 70 to 300K depth. Oceanic to Continental Plate Contact Deep – 300k+. Least destructive. Why?
  4. 4. 2013 HL Short Question
  5. 5. What are the effects of Earthquakes?  Page 24 Text
  6. 6. Haiti Earthquake • Cities in Haiti had large Shanty towns, these were badly damaged • Cholera spread rapidly after the earthquake • Haiti’s large debts meant that the country had no money to deal with earthquake damage • Earthquake hit just 25 KM from capital city – v little warning
  7. 7. 2008 Ordinary Level Question
  8. 8. Page 30 Text
  9. 9. Predicting Earthquakes • Examining Seismograph activity – lots of small quakes show that a major quake is on the way • Measuring Crustal Stress – drilling deep holes and measuring rock pressure • Lasers – used to measure ground movement • Radon Gas – rocks under stress emit more Changes in oil/water levels in wells – rising levels = more pressure • Unusual animal behaviour – some animals are more sensitive to P-Waves
  10. 10. 2013 Higher Level Essay & marking Scheme
  11. 11. • Spring loaded foundations • Shatterproof Glass in windows • Flexible joints in buildings – buildings can flex under pressure • More supports on each floor • Furniture and loose items to be secured
  12. 12. You are marked on the number of Significant, Relevant Points you have in your essay. Do not waffle, it only wastes time. Diagrams can be used to get SRPs Key to high marks is to read the question carefully and underline keywords “Explain with reference to examples you have studied, how the theory of plate tectonics helps to explain the distribution of earthquakes around the world” Essay writing in Geography
  13. 13. “Explain with reference to examples you have studied, how the theory of plate tectonics helps to explain the distribution of earthquakes around the world” Question asks about distribution In plain English, “Why do earthquakes happen where they happen” NOT “How do earthquakes happen” Reading the Question
  14. 14. Wrong approach “Earthquakes are caused by rocks slipping past each other. This causes shockwaves to spread out from the focus which cause great damage to buildings. Earthquakes give off P waves, S waves and Surface waves and surface waves are the most damaging. When an earthquake happens underwater it can cause a Tsunami which can cause floods like in Japan etc etc etc............ No mention of Plate Tectonics or of where earthquakes happen. Just general discussion. No relevance to question.
  15. 15. Right Approach “The theory of Plate Tectonics tells us that the Earth’s crust is divided into several plates. It also tells us tells us that plates can collide (destructive boundary) or scrape past each other (constructive boundary). When this happens, Earthquakes can occur. The Plates are moving because of convection currents in the Earth’s mantle which drag the plates around. Thus earthquakes are unlikely to occur in areas like Ireland which are far from plate boundaries. Areas like California are on the boundary of two plates (North American and Pacific) and therefore experience frequent Earthquakes .........”

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