<p>NAME:______DATE:______</p><p>Study Guide for Chapter 4 Test </p><p>1. Who was Alfred Wegener? What was his hypothesis of Continental Drift? - Alfred Wegener was a German scientist who hypothesized that he continents have been moving parallel to Earth’s surface for millions of years. His hypothesis was called the Continental Drift Theory. </p><p>2. Who was Harry Hess? - Harry Hess was an American geologist who was responsible for the seafloor spreading theory. He explained that the seafloor is spreading due to constant magma deposits at the mid-ocean ridges. </p><p>3. Mid-Ocean Ridges: Where are the young rocks and where are the old rocks? - The young/new rocks are right near the ridges. The older rocks are far from the ridges. </p><p>4. Define lithosphere. - Lithosphere is the cool, rigid layer of Earth made up of the crust and the upper mantle.</p><p>5. Where do the lithospheric plates float on top of? - The Mantle </p><p>6. What is a magnetometer? - It is an instrument that measures Earth’s magnetic fields and polarity.</p><p>7. What was Pangaea? - Ancient super continent that Wegener hypothesized exited 250 million years ago. </p><p>8. When did Wegener believe Pangaea break apart? - Wegener said Pangaea started to break apart 200 million years ago. </p><p>9. What evidence did Wegener use to back up his hypothesis? (rocks, plants, mountain ranges, climate. etc.) Explain each one.</p><p>- Rock types and Mountain ranges: Wegener explained that the same rock types and matching mountain ranges were found on different continents. - Fossil evidence: Plant (Glossopteris) and animal fossils matched up on continents that are really far away from each other today - Climate: Sedimentary rocks recorded evidence of plant decay, as well as glacial scratches, that show present day continents with warm climates used to have cold climates before - Fit of the continents: Wegener showed that the continents fit together like puzzle pieces. </p><p>10. What are mid ocean ridges? - Underwater mountain ranges and volcanoes that spread across our plant. </p><p>11. What is the process of seafloor spreading? - Convection currents and pressure in the mantle force magma to rise up and escape at the mid ocean ridges. This causes new seafloor to form, pushing away the old rocks/the old seafloor. </p><p>12. How fast is the sea floor moving? - very slowly, only a few centimeters pre year </p><p>13. How do scientist study the seafloor? What is used to do this? - Scientists use seafloor drilling and sonar technology to study the seafloor and dig up samples of rocks. </p><p>14. What are lithospheric plates? - Large, brittle pieces of Earth’s outer shell.</p><p>15. What is the theory of plate tectonics? - This theory states that the lithospheric plates are slowly moving parallel to Earth’s surface as seafloor spreading occurs </p><p>16. What are ocean trenches? - Large trenches in the ocean where old slabs of rocks are pulled back into the mantle, recycling the seafloor </p><p>17. What is the relationship between ocean trenches and plate boundaries? What happens at these sites? - Ocean trenches are usually located at plate boundaries. At these sites, we have earthquakes and volcanic eruptions. </p><p>18. What are the 2 types of lithosphere plates? Give 3 facts about each one - Oceanic lithosphere: thin, but dense. It is made of basalt and gabbro. - Continental lithosphere: thick, but less dense. Made of granite and gneiss 19. What are convection currents in the mantle? What is their role in seafloor spreading? - Convection currents move the molten rocks in the mantle around, pushing the colder rocks up, bringing the hotter lava down. This cycle pushes the lava upward, where it escapes from the seafloor at the mid ocean ridges, creating new seafloor</p><p>20. Differences in DENSITY cause hot, melted rocks in the asthenosphere to rise up.</p><p>21. What are some sources of heat in the mantle? - molten rocks - radioactive decay - convection currents </p><p>22. What is a slab? How is it related to seafloor spreading? - A plate that sinks back into the mantle. It gets rid of old seafloor as the new ones form. </p><p>23. What is ridge push? - the force of gravity pushes the plate downward and away from the mid ocean ridges. </p><p>24. What is slab pull? - An action where large pieces or rocks are pulled back into the mantle, recycling the old seafloor rocks. </p><p>25. What does GPS stand for? How does it work? - Global Positioning System - The network of satellites determine locations on earth by sending radio signals to receivers on Earth </p>