See Figure 3.19 41. List three major features of the theory of plate tectonics. Such features may be observations or mechanisms. Using the diagram, explain how magnetic reversals are used to support the theory of plate tectonics. See figure 3.29.
Magnetic signals record the direction of the earth s magnetic field at the time the rocks formed.
Magnetic reversals are recorded in rocks of the same age and distance from either side of a spreading center. Because an alternating pattern is observed and the age of the reversals increasies away from the spreading center, we deduce that the rocks must have formed at the ridge and spread away from it as new rock formed. On the following diagram showing shallow and deep earthquakes around the world, identify the subduction zones. See figure 3.10. The subduction zones are shown by deep earthquakes.