Tectonic Plates Test Study Guide Answers

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1 Tectonic Plates Test Study Guide Answers Weathering and Erosion 1. What is the difference between weathering and erosion? Weathering is the breakdown of earth materials and erosion is the movement of earth materials. 2. Give an example of chemical and physical weathering. Chemical weathering: Acid Rain, Oxidation (Rust), Hydrolysis, Carbonation, Plant Acids Physical weathering: Abrasion, Ice Wedging, Thermal expansion, Plants and animals 3. What are the four agents of erosion? Wind, water, glaciers, gravity Tectonic Plates 1. Describe the difference between the crust, mantle, and core. Crust Thin, brittle layer on the outside of the earth Mantle Semi solid, malleable inner layer Core Center made of iron and nickel 2. How is the inner core different from the outer core? Inner core is solid and outer core is liquid. 3. Describe the difference between the asthenosphere and the lithosphere. Lithosphere is the crust and a tiny bit of upper mantle. The lithosphere is solid and brittle. This is where the tectonic plates are located. The asthenosphere is malleable. This is the layer that the tectonic plates float on. 4. Describe what types of plates are involved at a subduction zone and describe what would most likely form there. One type of subduction zone occurs when oceanic crust goes underneath continental crust. Volcanoes and mountain ridges would be found on land. Another type of subduction zone occurs when old oceanic crust sinks underneath young oceanic crust. You would find an island arc (islands with active volcanoes) at this type of location. 5. Describe the plate motion and events that would usually occur at a transform boundary. At a transform boundary plates slide past one another. Earthquakes are common at these boundaries. Fault lines are also visible sometimes.

2 6. Describe how mountains are formed. Mountains are formed when two pieces of continental crust converge. 7. Describe what happens at a divergent boundary on land and in the ocean. A divergent boundary occurs when two plates are moving away from one another. On land this forms a rift. Sometimes there is a lake in the middle of the rift. It is also common to find volcanoes on the edges of rifts. In the ocean seafloor spreading occurs and new crust is created. Many times an ocean ridge is visible. 8. What causes the tectonic plates to move? Convection currents in the mantle. 9. What are the three main pieces of evidence that were used to support Wegener s theory of continental drift? Similar fossils found on different continents Continental coastlines fit together like a puzzle Similar geologic features (mountain ranges) 10. Describe how islands formed above hot spots and island arcs are different. Hot spots occur when magma from the mantle punches a hole through the crust. When the plate moves different islands are formed over the hot spot. Only the island currently above the hot spot would have active volcanic activity. Island arcs are formed when a piece of old oceanic crust is subducted below a piece of young oceanic crust. Volcanoes are formed and eventually grow into a string of islands. Multiple islands in island arcs have active volcanic activity. Volcanoes 1. Describe the characteristics of a stratovolcano or composite volcano. What type of magma does it have? Composite volcanoes are composed of intermediate to felsic magma and they are often very steep. They usually have an explosive eruption due to the extreme viscosity of the lava creating high pressure. 2. Describe the characteristics of a shield volcano. What type of magma does it have? Shield volcanoes are large but not very steep. They have a non explosive eruption because the mafic magma has a low viscosity is less pressure builds up in the volcano. 3. Describe the characteristics of a cinder cone volcano. Cinder cone volcanoes are small and coned shape. They are often steep and grow from a very rapid eruption process. Many times these are located next to shield volcanoes. 4. What does the explosiveness of a volcano depend upon? It depends on the amount of gas in a volcano and the viscosity of the

3 magma. The greater the viscosity and the more mass there is the more pressure builds up in the volcano. The greater the pressure, the greater the eruption. 5. What is viscosity? Name a liquid that has a high viscosity and a low viscosity. Viscosity is a liquid s ability to resist flow. A liquid that has a high viscosity is honey. A liquid that has a low viscosity is water. 6. Felsic lava/magma has a high viscosity and a high amount of silica. 7. Mafic lava/magma has a low viscosity and a low amount of silica. 8. Describe what pyroclasts are. Pyroclasts are small pieces of rock and/or dust that explode out of a volcano when it erupts. 9. Explain why composite volcanoes often have steep slopes and explosive eruptions. Composite volcanoes often have steep slopes because they are made of felsic magma. Felsic magma has a high viscosity and does not flow far from the center of the volcano before it hardens. They often have explosive eruptions because their highly viscous felsic magma builds up a lot of pressure before the volcano erupts. 10. Explain why shield volcanoes often have gently steeping slopes and less explosive eruptions. Shield volcanoes do not have steep slopes because they are made of mafic magma that has a low viscosity. This type of magma flows far from the volcano before it hardens. They often have less explosive eruptions because their low viscosity magma does not build up as much pressure before the volcano erupts. Earthquakes 1. What is a P wave and what are some of its properties? Draw one below. A P wave is also called a primary wave or a compression wave. It travels very quickly and can travel through liquids and solids. Click here to see an animation of a p wave and s wave. 2. What is an S wave and what are some of its properties? Draw one below. An S wave is also called a secondary wave. It travels slower than a p wave and can only travel through solids. Click here to see an animation of a p wave and s wave. 3. What is a normal fault? Draw one below. A normal fault is formed at a divergent plate boundary. hanging wall slips and falls under the footwall. The

4 4. What is a reverse/thrust fault? Draw one below. A reverse/thrust fault is formed at a convergent plate boundary. The hanging wall is pushed up and over the footwall. 5. What is a strike slip fault? Draw one below. A strike slip fault is formed at a transform plate boundary. Two plates slide past one another in opposite directions. 6. Define each of the following terms: foreshocks aftershock, mainshock. Foreshocks the small earthquakes that occur before the mainshock. Aftershocks the small earthquakes that occur after the main shock. Mainshock the earthquake that has the largest magnitude. 7. Describe how potential energy is built up and then released during an earthquake. Potential energy is built up when forces are pushing plates against one another. Because rocks are jagged they become hung up and do not move right away. When the rocks finally slip and release all of the pressure that has been building up, the potential energy is transformed into kinetic energy when an earthquake occurs. 8. What is the difference between the hanging wall and the footwall? Hanging wall the crust located above the fault line. Foorwall the crust located below the fault line. 9. What is the difference between the focus and the epicenter of an earthquake? The focus is where the earthquake originates underground. The epicenter is the spot just above the focus on the Earth s surface. 10. Look at the seismogram and the S P wave Travel Time curve on the back of this page. First of all, when does the S wave arrive according to the seismogram? Second of all, how far is the location where that seismogram was taken away from the epicenter of the earthquake? What additional information would you need to determine the exact location of the earthquake epicenter? First, students have to find when the S wave arrived at this location. The S wave is the second wave that shows up on a seismogram (the first is the P wave). As you can see below the S wave arrived at about 39 seconds. Next students have to use the Travel Time graph. When you look at what distance corresponds with 39 seconds you should end up with 390 kilometers. In order to find the exact location of the earthquake epicenter you would need seismograms from at least

5 two other cities.