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Name: ____Caleigh Kehoe_______ Learning Unit 3: Volcano Review Ques=ons This assignment is designed to assess your understanding of Unit 3 and includes some of the Ques=ons for Review at the end of Chapters 6 and 7 from your text plus a few addi=onal ques=ons. Each ques=on 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 evalua=on and grading through the assignment tab by or before the due date. 1. In what tectonic environments to volcanic erup=ons typically occur? Volcanos typically occur at either seduc=on zones, at riXing sea floor spreading zones, at divergent boundaries or at hot spots. 2. What changes in heat and pressure are necessary to melt rock and create magma? There will be high temperatures and pressure causing rocks to become liquid form to then create magma, as this is deep inside the earth. 3. How does felsic (rhyolite) magma form in the line of arc volcanoes like the Cascades? The felsic (rhyolite) is formed when basalt magma rises from above the subduc=on zones slab melts con=nental crust. 4. What are the two most-abundant gases in magmas? The two most-abundant gases in magmas are water vapor and carbon dioxide. 5. What factors influence the violence or style of an erup=on? The main factors of violence of erup=on are the amount of =me since the last erup=on, the viscosity, or thickness, of the magma, and the gas content within the magma. 6. What proper=es of mafic magma control its erup=ve behavior? It is characterized by low silica and low gas content; the erup=ons have low V.E.I and the magma comes from divergent boundaries. 7. What proper=es of felsic/intermediate magmas control their erup=ve behavior? It is characterized by high silica and high gas content; the eruptions have high V.E.I and the magma comes from convergent boundaries.8. What causes differences in viscosity among the major magma types? Three factors that affect magma viscosity are temperature, composi=on, and presence of dissolved gases 9. 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. A pyroclas=c flow surge blasted laterally and flahened forests. 10.Which of the hazards of volcanoes kill more people than any other? Why are they so dangerous? Pyroclas=c flows are more dangerous due to being fast moving and destruc=ve. Lava flows are very slow moving and cover a small area, posing lihle threat to human life. 11.Why do landslides some=mes trigger explosive erup=ons? A landslide may reduce pressure on shallow magma=c and hydrothermal systems, resul=ng in explosions ranging from minor steam explosions to enormous steam- and magma-driven directed blasts, by elimina=ng a major por=on of the volcano's cone. 12.Which gas is heavier than air, collects in low areas, and can asphyxiate people or animals if it is in high concentra=ons? Due to the fact that carbon dioxide is heavier than air, it may flow into low-lying areas and collect in the soil. Carbon dioxide gas concentra=ons in certain places can be deadly to people and animals. 13.An extremely large volcano with very gentle slopes is likely to be what kind of volcano and is likely to have originated from what composi=on magma (felsic, intermediate, mafic)? A shield volcano is most likely to be originated from basalt lava flows. Shield volcano gets formed by low viscosity magma. 14.A large, steep-sided volcano is likely to be what kind of volcano and is likely to have originated from what composi=on magma (felsic, intermediate, mafic)? A large, steep-sided volcano is likely to be a stratovolcano and is likely originated of intermediate to felsic. 15.Why do stratovolcanoes have steeply sloping sides but shield volcanoes have very gently sloping sides? A shield volcano has gently sloping slides because the lava cone is formed by the basal=c volcanism and basalt is more viscous. A stratovolcano has a steeply sloping slides layered composite cone, it called a composite cone as it formed partly by the explosive erup=on and partly by the flow of lava.16.What is the driving force behind the explosive ac=vity of a cinder cone? When rising basal=c magma collides with nearby groundwater, escaping steam coughs cinders of bubbling molten lava out of the vent or summit crater. 17.Yellowstone Park has two huge calderas, each more than 20 km across. How do such calderas form? Ejec=on of a large volume of magma oXen causes collapse into the magma chamber. 18.What signs (precursors) suggest that a volcano may be preparing to erupt? No=ceable steaming or fumarolic ac=vity and new or enlarged areas of hot ground. Subtle swelling of the ground surface. Small changes in heat flow. Changes in the composi=on or rela=ve abundances of fumarolic gases. 19.Harmonic tremors recorded on seismographs near volcanoes are generally interpreted as: They form when fluid basal=c magma rises along a fracture and encounters ground water. The steam generated blows fragments of lava violently in the air, which solidifies and falls as cinders along the vent forming an oval


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Montclair EAES 104 - Volcano Review Questions

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