Plate Tectonics

• 1. Plate Tectonics

2. Major Tectonic PlatesBoundaries betweenplates are just lines onmaps, but the stressescaused by moving platesaffect vast areas of rocknear the boundaries.Major Earthquakes Compare the two figures. What relationship is there between the tectonic plate boundaries and earthquakes? 3. Normal FaultA normal fault drops rock on one side of the faultdown relative to the other side. Take a look atthe side that shows the fault and arrowsindicating movement. See the block farthest tothe right that looks kind of like a foot? Thats thefoot wall. Now look at the block on the otherside of the fault. See how its resting or hangingon top of the foot wall block? Thats the hangingwall.Now, consider this: if we hold the foot wallstationary, gravity will normally want to pull thehanging wall down, right? Faults that move theway you would expect gravity to move themnormally are called normal faults! Not so hard,is it?Take a look where the fault has ruptured theEarth surface. Notice that movement along thefault has produced an elongate cliff? That fault-generated cliff is called a fault scarp. 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. Heres 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? Thats the foot wall. Now look at the block on the other side of the fault. See how its resting or hanging on top of the foot wall block? Thats 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. 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. Fault Illustrations Fault MovementNormal MovementReverse and Thrust FaultsEarthquake Focus 7. Fault Movement ActivityABCopy and complete the following Table Photo Fault Land HumanAffect AffectAB CC 8. Earths Crust 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 earthquakeaffect peoples immediatesurroundings in Nelson (insidehouses, buidlings) ?2. In what way will an earthquakeaffect our local landscape?3. What can we do to minimise thedamage that an earthquakemay cause? 10. Earthquake Location Patterns Study this map to answer thefollowing 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. Local Fault Lines The Nelson urban area lies within the most tectonically active zone of New Zealand. 12. Richmond & StokeGRAMPIAN88 FAULTWAIMEAFLAXMOREHESLINGTONThe faults looking across Richmond towards Mackays Bluff.The Waimeai, Grampians and Flaxmore Faults are clearly seen 13. Waimea Fault WAIMEA 88 FAULT JENKINSBISHOPDALE The faults near the Brook Street volcanics 14. Nelson AreaGRAMPIAN88 FAULTWAIMEAFLAXMOREBISHOPDALEOver Nelson College and Bishopdale. There are several faults in this area. 15. Sharland Fault FLAXMORE SHARLAND Sharland Hill over to the Boulder Bank. 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 localarea. 3. Explain how earthquakes relate to faultlines. 4. Research how earthquakes haveaffected the local area.