Name: KEY Unit III: The Lithosphere – Section 2 Volcanic Thermal Processes Earth & Environmental Systems Science Volcanic Processes Study Guide
Background Knowledge – Layers of the Earth 1. List the layers of the Earth starting and the surface and describe if they are solid or liquid in state. Continental Crust/Lithosphere - solid Oceanic Crust/Lithosphere - solid Mantle/Asthenosphere - liquid Outer Core - liquid Inner Core - solid 2. What data do we measure in order to determine the thickness of the layers? We use seismic data and can measure the speed and timing of the earthquakes in order to calculate the distance or thickness of the layers. 3. The plates of solid lithosphere ride on top of the asthenosphere. 4. Fill out the following chart: Type of Density Thick/Thin Type of Rock Lithosphere: Continental Crust Low density due to Thick Granite high volume Oceanic Crust High density due to Thin Basalt low volume
Thermal Process – Convection 1. The movement of tectonic plates is driven by what thermal process in the mantle? Tectonic plates including continental and oceanic crust move due to convection currents in the mantle that transfer heat from the outer core to the mantle and then to the crust. 2. Define the term convection: Convection is a mixing due to unevening heating that causes a difference in the temperature and density of the material that makes a rising or sinking motion of the fluid. 3. True or False: Changes in the mantle material’s heat and density is causes convection currents. 4. How does a lava lamp represent convection currents in the mantle? The light bulb heats the material unevenly just like the outer core heats the mantle unevenly. As the temperature rises, the volume expends, creating a material that has a low density and a rising effect. As the material moves away from the heat source, it cools, condenses, and sinks.
Location of Volcanic Activity 1. At a divergent plate boundary, volcanoes form along which feature on the ocean floor? Mid-Ocean Ridge (Rise) 2. What is an underwater mountain chain called? Ocean Ridge 3. At a mid-ocean ridge, where would the hottest crust temperature be located? At the center of the mid-ocean ridge where mantle material is cooling to form new crust.
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Name: KEY Unit III: The Lithosphere – Section 2 Volcanic Thermal Processes Earth & Environmental Systems Science Volcanic Processes Study Guide
4. Describe the trends of the ocean floor age, sediment thickness, and heat flow as you move away from the center of the mid-ocean ridge. As you move away from the center of a mid-ocean ridge, the ocean floor gets older, the sediment on top of the floor gets thicker, and the heat flow decreases or gets colder proving that the center of the Mid-Ocean Ridge is the location of newly formed oceanic crust due to mantle convection currents. 5. What is one similarity and one difference between a rift valley and a mid-ocean ridge? Rift Valleys and Mid-Ocean Ridges are locations where the crust is spreading apart due to mantle convection currents and new crust is being formed. Rift Valleys are tearing continents apart and may be covered by a small inlet and a sea. Mid- Ocean Ridges are tearing oceanic crust apart to make new oceanic crust and are covered by vast oceans. 6. Why does oceanic crust sink beneath the continental crust at subduction zones? Oceanic crust is more dense than continental crust and will sink or be over-ridden by the continental crust. The oceanic crust is melted and recycled back into the mantle. 7. Compare the plate motion at a trench to the plate motion at a mid-ocean ridge. At a mid ocean ridge, oceanic crust is moving outward to make new oceanic crust. At a trench a collision occurs where oceanic crust is being subducted by continental crust, and the oceanic crust is melted an recycled back into the mantle. 8. Draw in the convection currents based on the features of the mid-ocean ridge and trench:
9. What feature is formed when a piece of continental crust and a piece of oceanic crust collide? The oceanic crust will be subducted because it is more dense. When the plates collide, friction creates a pulling effect on both pieces of crust and a deep oceanic trench is formed. 10. What feature is formed when two pieces of oceanic crust collide? One piece of oceanic crust will be subducted. When the plates collide, friction causes the subducting plate to melt quickly, becoming less dense and sending magma upward. This magma cools and solidifies as a volcanic island arc. 11. Describe how hot spot volcanoes create and chain of islands on how that can predict plate movement. The small hot spot stays stationary (at the same latitude and longitude) and creates a shield volcano as the magma breaks through the thin oceanic crust. This process continues to create a larger and larger volcano. The plate moves and will take the volcano with it, eventually moving it
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