Each statement represents a primary learning objective for parts of this unit. After you complete the unit, you should be able to:

• Summarize the view that most geologists held prior to the 1960s regarding the geographic positions of the world’s ocean basins and continents.

• List and explain the evidence Wegener presented to support his continental drift hypothesis.

• List the major differences between Earth’s lithosphere and asthenosphere and explain the importance of each in the plate tectonics theory.

• Sketch and describe the movement along a divergent plate boundary that results in the formation of new oceanic lithosphere.

• Compare and contrast the three types of convergent plate boundaries and name a location where each type can be found.

• Describe the relative motion along a transform fault boundary and locate several examples of transform faults on a plate boundary map.

• Explain why plates, such as the African and Antarctic plates, are increasing in size, while the Pacific plate is decreasing in size.

• List and explain the evidence used to support the plate tectonics theory.

• Describe two methods researchers use to measure relative plate motion.

• Describe plate–mantle convection and explain two of the primary driving forces of plate motion.