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Name ___________________________ Date _________ Period 1 2 3 4 5 6 Plate Tectonics One of the major questions with the Theory of Continental Drift is how does it work? We live on a dynamic Earth, in which about twenty 60-mile thick lithospheric plates move about on the fluid upper mantle. The plates jostle with each other, some hit each other head on, some go under one another, and some just slide by each other. Most of the volcanoes and earthquakes on Earth happen where these plates meet. Plate tectonics emphasizes that new ocean crust is produced at the midocean ridges. This new crust begins to spread to either side of the ridge. As it spreads, it dives under another plate and is subducted back into the upper mantle. At some geologic time in the future, the recycled crust appears again at a mid-ocean ridge. There are three types of plate interaction • Divergent Plate Boundaries • Convergent Plate Boundaries • Transform Plate Boundaries Divergent Plate Boundaries are where plates are moving away from each other. This movement is found along the midocean ridges where new crust material is being created. • Type II Ocean – Continental: when ocean crust subducts under continental crust forming mountain chains and volcanic activity • Type III Continental – Continental: when two continental plates meet and buckle up forming large mountains. Transform Plate Boundaries are when plates move side by side with each other resulting in frequent earthquakes. Convergent Plate Boundaries are where one plate dives (subducts) under less dense crust to be recycled back into the asthenosphere. There are three types of convergent plate boundaries: • Type I Ocean – Ocean: when the ocean crust of two plates meet usually forming island arcs Name ___________________________ Date _________ Period 1 2 3 4 5 6 Fig 1: Global Lithospheric Plates’ Relative Motion and Speed Data Analysis 1. Look at Fig 1: Global Lithospheric Plates’ Relative Motion. 2. Determine what type of plate boundary exists between each of the two plates in Table 1. 3. Describe the type of stresses that occur at the plate boundaries in Table 1. Use the three choices diagramed below. Plate Boundary Boundary Type Stresses North American Plate and the Pacific Plate near California Nazca Plate and the South American Plate South American Plate and the African Plate Pacific Plate and the Nazca Plate Juan DeFuca Plate and the Pacific Plate Juan DeFuca Plate and the North American Plate Australian Plate and the Eurasian Plate North American Plate and the African Plate Pacific Plate and the Philippine Plate Indian Plate and the Eurasian Plate Questions 1. Where does the overwhelming amount of seismic activity occur on the Earth’s surface? 2. Explain why the term recycling is an excellent description of plate tectonics. 3. Explain how tectonic plate movement could create another supercontinent like Pangaea. 4. If the Earth’s core provides the heat that drives plate tectonics, then what will eventually happen as the Earth’s core cools down over billions of years? 5. What are the various ways in which lithospheric plates interact with each other as they move around on a dynamic Earth?