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Montclair EAES 104 - Volcano Review Questions

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Name: __Angel Barkley_____Learning Unit 3: Volcano Review QuestionsThis assignment is designed to assess your understanding of Unit 3 and includes some of the Questions forReview at the end of Chapters 6 and 7 from your text plus a few additional questions. Each question can be answered in one to two sentences. Please limit yourself to a maximum of three sentences. Access the assignment, complete it with ANSWERS IN A DIFFERENT COLOR FONT as a separate file, and send it back for evaluation and grading through the assignment tab by or before the due date. 1. In what tectonic environments to volcanic eruptions typically occur?Volcanoes typically occur at subduction zones, divergent plate boundaries, or hot spots. 2. What changes in heat and pressure are necessary to melt rock and create magma?In order to create magma the heat needs to be increased and the pressure needs to be decreased. 3. How does felsic (rhyolite) magma form in the line of arc volcanoes like the Cascades?The subduction zone forms felsic to intermediate magma. 4. How does lava differ from magma?Lava occurs when the liquid magma is released after the eruption. It is considered lava when it reaches the surface. 5. What are the two most-abundant gases in magmas? The two abundant gases are water vapor and carbon dioxide. 6. What factors influence the violence or style of an eruption? The factors that influence the violence or style of an eruption is the amount of time sincelast eruption, gas content of magma, and thickness or magma. 7. What properties of mafic magma control its eruptive behavior?Low water content creates low gas content and low silicon and oxygen content create low viscosity are apart of the eruptive behavior. 8. What properties of felsic/intermediate magmas control their eruptive behavior?High water content creates high gas content and high silicon and oxygen and content make high viscosity are properties of felsic/intermediate magma.9. What causes differences in viscosity among the major magma types?Different percentages of silica and compositions cause the viscosity of magma. The more viscous the magma, the higher the percentage of silica. 10. If you visit Mount St. Helens, Washington, you will see thousands of trees lying on the ground, all parallel to one another. Explain how they got that way.The lateral blast from the beginning of the eruption made a pyroclastic flow, that knocked them all down, pointing away from the blast. 11. Which of the hazards of volcanoes kill more people than anything else? Why are they so dangerous?The most fatal hazard of volcanoes is the Pyroclastic Flow because essentially is a cloud of hot volcanic gases and debris that can range in size. It is able to wipe a whole city out like Pompeii. 12. Why do landslides sometimes trigger explosive eruptions?Landslides allow for heavy debris to fall into bother an volcano and shake it up almost like a soda can until it explodes.13. Which gas is heavier than air, collects in low areas, and can asphyxiate people or animals if it is in high concentrations?Carbon dioxide is the gas that can asphyxiate people or animals in high concentrates.14. An extremely large volcano with very gentle slopes is likely to be what kind of volcano and is likely to have originated from what composition magma (felsic, intermediate, mafic)? A Shield volcano is a large volcano with gentle slopes and has mafic type of magma. 15. A large, steep-sided volcano is likely to be what kind of volcano and is likely to have originated from what composition magma (felsic, intermediate, mafic)? A large steep sided volcano is likely to be composite volcano also known as a stratavolcano with mafic magma.16. Why do stratovolcanoes have steeply sloping sides but shield volcanoes have very gently sloping sides?Shield volcanoes have persistent basalt lava within a small area that eventually build a gently sloping pile of thin flows. Stratovolcanoes have steep sloping sides because themagma slowly flow down the slopes and cool and solidify. 17. What is the driving force behind the explosive activity of a cinder cone? The Cinder Cone erupt where rising basaltic magma meet surface ground and then the steam creates bubbles explode molten lava out the vent. 18. Yellowstone Park has two huge calderas, each more than 20 km across. How do such calderas form?A Caldera is a feature formed by the collapsing of the volcano itself creating a special form of a volcanic crater. 19. What signs (precursors) suggest that a volcano may be preparing to erupt?Some precursors that suggest a volcano may erupt are elevation change, slope steepness, and bulging on volcano flanks. 20. Harmonic tremors recorded on seismographs near volcanoes are generally interpreted as:The indication of magma movement and recording that determines many


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