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Plate Tectonics

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Plate Tectonics

  1. 1. Plate Tectonics
  2. 2. Major Tectonic Plates Boundaries between plates are just lines on maps, but the stresses caused by moving plates affect vast areas of rock near the boundaries. Major Earthquakes Compare the two figures. What relationship is there between the tectonic plate boundaries and earthquakes?
  3. 3. Normal Fault A normal fault drops rock on one side of the fault down relative to the other side. Take a look at the side that shows the fault and arrows indicating movement. See the block farthest to the right that looks kind of like a foot? That’s the foot wall. Now look at the block on the other side of the fault. See how it’s resting or hanging on top of the foot wall block? That’s the hanging wall. Now, consider this: if we hold the foot wall stationary, gravity will normally want to pull the hanging wall down, right? Faults that move the way you would expect gravity to move them normally are called normal faults! Not so hard, is it? Take a look where the fault has ruptured the Earth surface. Notice that movement along the fault has produced an elongate cliff? That fault- generated cliff is called a fault scarp.
  4. 4. Reverse Fault We classify faults by how the two rocky blocks on either side of a fault move relative to each other. The one you see here is a reverse fault. Along a reverse fault one rocky block is pushed up relative to rock on the other side. Here’s a way to tell a reverse fault from a normal fault. Take a look at the side that shows the fault and arrows indicating movement. See the block farthest to the right that is shaped kind of like a foot? That’s the foot wall. Now look at the block on the other side of the fault. See how it’s resting or hanging on top of the foot wall block? That’s the hanging wall. Think about this: if we hold the foot wall stationary, where would the hanging wall go if we reversed gravity? The hanging wall will slide upwards, right? When movement along a fault is the reverse of what you would expect with normal gravity we call them reverse faults!
  5. 5. Strike-slip Fault Strike-slip faults have a different type of movement than normal and reverse faults. You probably noticed that the blocks that move on either side of a reverse or normal fault slide up or down along a dipping fault surface. The rocky blocks on either side of strike-slip faults, on the other hand, scrape along side-by-side. You can see in the illustration that the movement is horizontal and the rock layers beneath the surface haven't been moved up or down on either side of the fault. Take a look where the fault has ruptured the Earth surface. Notice that pure strike-slip faults do not produce fault scarps. There are other tell-tale changes in the landscape that signal strike-slip faulting.
  6. 6. Fault Illustrations Fault Movement Normal Movement Reverse and Thrust Faults Earthquake Focus
  7. 7. Fault Movement Activity A B Copy and complete the following Table Photo Fault Land Human Affect Affect A B C C
  8. 8. Earth’s Crust
  9. 9. Earthquakes The Nelson urban area lies within the most tectonically active zone of New Zealand. The area has experienced damaging earthquakes, those since European settlement being in 1848, 1868, 1893, 1929, and 1968. They could originate from local or distant fault movement. 1. In what ways will an earthquake affect people’s immediate surroundings in Nelson (inside houses, buidlings) ? 2. In what way will an earthquake affect our local landscape? 3. What can we do to minimise the damage that an earthquake may cause?
  10. 10. Earthquake Location Patterns Study this map to answer the following questions 1 What did scientists measure to make these maps? 2 What pattern do you observe? 3 Are the earthquakes more frequent and/or bigger in the North Island than the South Island? 4 In which place would you expect to see the greatest number of fault lines? 5 On the outline map of NZ, draw fault lines in where you think they run.
  11. 11. Local Fault Lines The Nelson urban area lies within the most tectonically active zone of New Zealand.
  12. 12. Richmond & Stoke GRAMPIAN 88 FAULT WAIMEA FLAXMORE HESLINGTON The faults looking across Richmond towards Mackay’s Bluff. The Waimeai, Grampians and Flaxmore Faults are clearly seen
  13. 13. Waimea Fault WAIMEA 88 FAULT JENKINS BISHOPDALE The faults near the Brook Street volcanics
  14. 14. Nelson Area GRAMPIAN 88 FAULT WAIMEA FLAXMORE BISHOPDALE Over Nelson College and Bishopdale. There are several faults in this area.
  15. 15. Sharland Fault FLAXMORE SHARLAND Sharland Hill over to the Boulder Bank.
  16. 16. Fault Line Activity In groups discuss the following questions: 1. What is a fault line? 2. List all the major fault lines in our local area. 3. Explain how earthquakes relate to fault lines. 4. Research how earthquakes have affected the local area.

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