Chapter 4 Plate tectonics Essay

Chapter 4 plate tectonics Need a Hint? 1.What evidence proved that South America, Africa, India, and Australia were once covered by glaciers? glacial deposits and rock surfaces scarred by glaciers 2. What happens when an oceanic plate converges with a continental plate? The denser oceanic plate slides under the less dense continental plate. 3. A divergent boundary is a boundary between two plates that __________. Move away from each other. 4.Do two colliding continental plates always cause volcanoes? Two colliding continental plates do not always cause volcanoes 5. What clue supported the continental drift theory? The puzzlelike fit of all the continents fossils of Mesosaurus, and similar rock structures on different continents support the continental drift theory. 6. What is the plate tectonic theory? the belief that Earth’s crust and upper mantle is broken into sections 7. What are strike-slip faults? Strike-slip faults occur where rocks on opposite sides of the fault move in opposite or the same directions at different rates. 8.Why was the discovery of no rocks older than 2 billion years old on the ocean floor so important? The discovery of no rocks older that 2 billion years old on the ocean floor proved the theory of seafloor spreading. 9. How do scientists explain the formation of underwater mountain ranges? Scientists believe seafloor spreading explains the formation of underwater mountain ranges. 10. How do scientists use sound waves to figure out the shape of the ocean floor? Scientists use sound waves to figure out the shape of the ocean floor because sound waves echo off the ocean floor – the longer it takes a sound wave to return to the ship, the deeper the water is. 11.How can crust disappear at the edge of a boundary? Crust can disappear at the edge of a boundary when new crust is being added to the other edge of the boundary. 12. What is the difference between normal faults and rift valleys? The difference between normal faults and rift valleys is that rift valleys are formed from normal faults. 13. Who first proposed the theory of continental drift? Alfred Wegener first proposed the theory of continental drift. 14. What is a magnetic field reversal? a magnetic field reversal is when Earth’s magnetic field leaves the north pole and enters the south pole 15. What do scientists believe is the force behind the plate tectonics theory? Scientists believe the force behind the plate tectonics theory is convection currents. 16. What is a transform boundary? A transform boundary is when two plates slide past one another, often forming fault lines. 17. How does the Mesosaurus fossil evidence support the continental drift theory? The Mesosaurus fossil evidence supports the continental drift theory because its unlikely that the Mesosaurus could swim between continents. 18. What is the lithosphere? The lithosphere consists of the plates that make up the crust and the upper part of the mantle 19.What tool does a scientist use to detect magnetic fields? Scientists use a magnetometer to detect magnetic fields. 20. What happens to rock around a subducting slab? Rock around a subducting slab goes under the other plate.