Chapter 1: Plate Tectonics Earth’s Layers Continents Changing Position Over Time Plates Moving Apart Plates Coming Together 100 100 100 100 200 200 200 200 300 300 300 300 400 400 400 400 500 500 500 500 This is a solid sphere of metal found in the center of the Earth. It is mainly made up of nickel and iron. The Inner Core The layer of the Earth made up of the crust and rigid rock of the upper mantle Lithosphere Although the word “asthenosphere” comes from the Greek word asthenes, meaning weak, it is not actually weak. How can it be characterized? layer of hotter, softer rock in the upper mantle. Solid lithosphere rests on it. Hot tar. Most large tectonic plates include two types of crust. What are these types of crust? Continental & Oceanic To explore the interior of the Earth, what must scientists study? They must study the energy from earthquakes or underground explosions. Alfred Wegener proposed this hypothesis to help explain Earth’s continents moving over time. Continental Drift Theory This supercontinent began splitting 200 million years ago. Pangaea What three pieces of evidence did Alfred Wegener use to support his hypothesis on the continents moving? And provide detail to at least one. Fossils- ancient reptile Mesosaurus had been discovered in South America and western Africa. Not found anywhere else. Climate- Greenland had once been near the equator and slowly moved to the Arctic circle. Geology- best evidence came from finding a type of rock that was in Brazil matched rock found in western Africa. Huge underwater mountain ranges that circle the Earth like the seams of a baseball. They are also formed from divergent boundaries. Mid-Ocean Ridges How does the age of the sea floor show that plates are moving? Rock is youngest near the ridge, and older farther away. Showing that older rock was carried away from the ridge some time ago. This is a boundary where plates are moving apart. What is the name of this boundary and where are most of them found? Divergent Boundary—in the ocean True or False. Mid-ocean ridges are the longest chain of mountains on Earth. True—Mid-Atlantic Ridge is the longest. What is a hot spot? an area where a column of hot material rises from deep within a planet’s mantle and heats up the lithosphere above it, often causing volcanic activity at the surface. Suppose a magnetic reversal occurred today. How would new rocks at midocean ridges differ from the rocks that formed last year? The magnetic minerals in the new rocks would be aligned in the opposite direction. Name and describe the three types of plate movement. 1. Divergent—moving apart 2. Convergent—pushing together/colliding 3. Transform—scraping past each other This is the process in which one plate sinks beneath another. Subduction True or False. Major geologic events occur at all three types of boundaries. True. These are like deep canyons that form as the ocean floor sinks. Deep Ocean Trenches There are 3 types of convergent boundaries. Please list all three and describe them briefly. Continental-continental collision: two plates carrying continental crust push together Oceanic-Oceanic subduction: one plate w/oceanic crust sinks Oceanic-Continental Subduction: occurs where crust sinks under continental crust. Please give an example of a transform boundary. San Adreas Fault—the Pacific plate and the North American plate are scraping past each other along the San Andreas Fault. Crust is not being formed or destroyed.