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Transcript
Chapter 3 Study Guide Section 1 continental drift Pangaea (supercontinent) fossil the hypothesis that the continents slowly move across Earth’s surface The name of the single landmass that began to break apart 200 million years ago and gave rise to today’s continents Preserved remains or traces of an organism that lived in the past Wegener’s hypothesis was that all the continents were once joined together in one landmass and have since drifted apart. The idea of the continents moving over Earth’s surface became known as continental drift. Alfred Wegener Evidence from Land Features Shapes of continents looked like a puzzle that would fit together Mountain ranges in South America and Africa line up Coal fields in Europe and North America line up Wegener could not identify the force that moved the continents, so most geologists of his time rejected the idea. Evidence from Fossils Evidence from Climate Glossopteris is a plant that lived 250 Fossils of tropical plants have been found million years ago. Glossopteris fossils on an island in the Arctic Ocean. These have been found in Africa, South plants only could have lived in a warm America, India, and Antarctica. climate. Fossils of the freshwater reptiles Wegener proposes that the island’s Mesosaurus and Lystrosaurus have climate changed because it moved toward been found in Africa and South the poles (away from the equator). America, which are now separated The plant only could have lived in a by oceans. warmer climate, closer to the equator. Section 2 An undersea mountain chain where new ocean floor is produced Mid-ocean ridge A deep valley or canyon along the ocean floor beneath which oceanic crust slowly sinks Deep-ocean trench toward the mantle The process by which molten material adds new oceanic crust to the ocean floor Sea-floor spreading The process by which oceanic crust sinks beneath a deep-ocean trench and back into Subduction the mantle at a convergent plate boundary Mid-Ocean Ridges- long chains of mountains rising from the ocean floor These ridges are the longest mountain ranges on Earth. Scientists mapped mid-ocean ranges using sonar. Mid-ocean ridges are found in all of Earth’s oceans. Sea-floor spreading adds more crust to the ocean floor. At the same time, older strips of rock move outward from the side of the ridge. Spreading begins at a mid-ocean ridge, which forms a crack in the oceanic crust Along the ridge, molten material rises, erupts, cools, and hardens into new rock. The new crust (rock) pushes older rock outward. Evidence from Ocean Material Rocks shaped like pillows have been found in the central valley of mid-ocean ridges. These rocks can only form when molten material cools quickly under water. Evidence from Magnetic Strips Evidence from Drilling Samples Magnetic minerals in rocks line up in Older rocks are found as you move the direction of Earth’s magnetic away from mid-ocean trenches. poles. The poles occasionally reverse The youngest rocks are always at which results in magnetic stripes on the center of the trenches. the ocean floor. The pattern is the same on both sides of the mid-ocean ridge. Chapter 3 Study Guide Section 3 A section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of Plate the oceanic and continental crust The theory that pieces of the lithosphere are in constant motion, driven by convection Plate Tectonics currents in the mantle A break in Earth’ crust along which rocks move Fault A deep valley that forms where two plates move apart Rift Valley Key Idea: Convection currents in the mantle are the forces that cause the plates to move. During subduction, gravity pulls the denser plate edges downward into the mantle. This pulls the rest of the plate, causing it to move. Key Idea: The slow and constant movement of Earth’s plates has changed Earth’s surface. the location of continents Scientists use satellites to the shape of oceans measure plate movements. causes earthquakes, volcanoes, mountain ranges, deep-ocean trenches Key Idea: Earth’s plates meet at boundaries. At each boundary, plates move in one of three ways. Divergent Boundary Convergent Boundary A plate boundary where two plates move away from each other A plate boundary where two plates move toward each other A plate boundary where two plates move past each other in opposite directions Transform Boundary Most occur at mid-ocean ridges where new crust is added during seafloor spreading When 2 oceanic plates converge, the more dense plate sinks below the less dense plate. Where pieces of Earth’s crust diverge on land, a rift valley occurs. Sides of plates are rocky and jagged, which holds the plates together When forces push them to move, earthquakes can occur, such as on the San Andreas fault in California. When a dense oceanic plate converges with a continental plate, it can push up the continental plate forming mountains (Andes Mtns.) and volcanoes When 2 continental plates converge, the collision squeeze the crust into high mountain ranges.