Plate Boundaries Worksheet Name ___________________ The crust of the Earth is broken into plates which are on the move due to convection currents below in the Asthenosphere layer of the Mantel. Plates that run into one another are called convergent. Plates that are spreading or moving away from one another are called divergent. Plates that are sliding by one another are called transform. Your job is to use the diagram below to complete the chart below on the different types of plate boundaries. * Label the Boundary/Margin type for the 3 diagrams on the left. * Draw some convection currents in the diagram above that would explain the hot spot and the divergent boundary. Convergent Motion (Describe the motion of one plate relative to another) Effect (Is it constructive or destructive to 1 or more of the adjacent plates?) Topography (What are the landforms that are associated with this type of margin?) Volcanic Activity? (Yes/No) Earthquake Activity? (Yes/No) Use your plate map to identify 2 places in the world with this type of plate boundary/margin Type of Margin/Boundary Divergent On land you see: In the ocean you see: Transform Usually you don’t really “see” a fault line at a transform margin. Sometimes you do. Seafloor Spreading and Magnetic Reversals Albert Einstein called the generation of Earth’s magnetic field one of the greatest mysteries in physics. Scientists are still not sure how the field is generated, though it is clearly related to the movement of molten iron in the liquid outer core. Even more puzzling is why the field switches back and forth between normal and reversed polarity. The measured strength of the magnetic field has dropped by 5-10% in the last 150 years, and less precise readings suggest it may have weakened by 25-50% over the last 5,000 years. Satellites have detected two areas in the mantle that appear to have reversed polarity. These data have led some to speculate that a magnetic reversal may be imminent. 1. Based on the diagram, how many times has the Earth's magnetic field reversed during the past four million years? 2. Approximately when did the current interval of normal polarity begin? 3. If there had been compasses four million years ago, which direction would compass needles have pointed? 4. Why are the magnetic stripes on the sea floor parallel to and symmetrical across the mid-ocean ridge?