Name: Joshua FernandezLearning Unit 3: Volcano Review QuestionsThis assignment is designed to assess your understanding of Unit 3 and includes some of the Questions for Review 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?- Divergent boundaries (rift valleys and mid ocean ridges), convergent boundaries (subduction of lithosphere)2. What changes in heat and pressure are necessary to melt rock and create magma?- Increasing heat of the subduction zone or decreasing pressure of at divergent boundaries3. How does felsic (rhyolite) magma form in the line of arc volcanoes like the Cascades?- Formed by mafic magma rising from the subduction of the oceanic slab that heats upthe felsic continental crust causing the continental crust to melt and form felsic magma4. How does lava differ from magma?- The difference is lava is magma that erupts onto the earth’s surface5. What are the two most-abundant gases in magmas? - CO2 and water vapor6. What factors influence the violence or style of an eruption? - Viscosity of magma, the higher the viscosity=more violent eruption. Amount of water, the more water= more gas7. What properties of mafic magma control its eruptive behavior?- The more viscous it is, the more eruptive it becomes, higher gas content, the more violent it becomes during eruption8. What properties of felsic/intermediate magmas control their eruptive behavior?- High gas content and high viscosity due to high silicon and oxygen9. What causes differences in viscosity among the major magma types?- The amount of silica, the more silica it has, the more viscous it becomes. 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.- They got that way because of the pyroclastic flow that knocked them down, as they’re all pointing away from where the blast came from11.Which of the hazards of volcanoes kill more people than any other? Why are they so dangerous?- Mudflows or lahars, because they are more common and can happen at any time. Its formed by the mixing of water with loose volcanic ash and debris and as it goes down, it gathers rocks.12.Why do landslides sometimes trigger explosive eruptions?- As there is a removal of load caused by the landslide, it decreases pressure on the gasses causing them to expand rapidly. 13.Which gas is heavier than air, collects in low areas, and can asphyxiate people or animals if it is in high concentrations?- CO2 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)? - It would be a shield volcano mafic lava flow15.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 stratovolcano of felsic/intermediate lava16.Why do stratovolcanoes have steeply sloping sides but shield volcanoes have very gently sloping sides?- Stratovolcanoes have steeply sloping sides because of the felsic/intermediate magmathat has more viscosity, shield volcanoes have low viscosity so it could travel more in distance.17.What is the driving force behind the explosive activity of a cinder cone? - Water from the ground becomes steam, expanding steam will blow basalt cinders out of the vent 18.Yellowstone Park has two huge calderas, each more than 20 km across. How do such calderas form?- Eruptions could be so violent that after the eruption ends, the volcano collapses into the empty magma chamber beneath leaving a crater called caldera19.What signs (precursors) suggest that a volcano may be preparing to erupt?- Some signs could be small earthquakes, increasing groundwater temperature, increasing gas emissions, and steam blasts. 20.Harmonic tremors recorded on seismographs near volcanoes are generally interpreted as:- moving
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