Volcanoes and Earthquake - Assignment Example

 Volcanoes and Earthquake 1. What is the definition of a volcano? A volcano refers to a conical hill or a mountain that has a vent or crater through which gases, lave, hot vapor, and rock fragments have left the interior of earth due to eruption (Gill, 2009). 2. List the layers of the Earth, from the crust to the core, as they are classified by chemical composition and briefly describe the composition of each layer. i. The crust, which consists of alumino-silicates and other chemical compounds, is the outermost layer of the Earth. ii. The mantle, which consists of ferro-magnesium silicates, is the middle layer of the Earth. iii. Core, which consists of an alloy of iron metal and nickel, is the innermost region of the Earth. 3. List the layers of the Earth, from the crust to the core, as they are classified by physical properties and briefly describe the physical properties of each layer. i. Lithosphere, which consists of the solid and rocky layer of the Earth, is the crust and top section of mantle. ii. Asthenosphere, which consists of the weak layer of ductile solid material, lies under the lithosphere. iii. Mesosphere, which consists of the rigid rock material, lies under the Asthenosphere. iv. Outer core, which consist of liquid materials, lies under the mesosphere. v. Inner core, which consists of the solid materials, is the innermost portion of the Earth. 4. What is mantle convection? Mantle convection refers to the slow creeping movement of the solid in the silicate mantel of the Earth due to convectional currents, which conduct heat from the Earth’s interior to the surface (Gill, 2009). The mantle convection may lead to plate tectonics, volcanism, and earthquakes or tremors. 5. What are the 3 types of plate boundaries, and what kind of movement occurs at each boundary? i. Divergent plate boundary, which involves the movement of two tectonic plates away from each other. ii. Convergent plate boundary, which involves the movement of two tectonic plates toward each other, leading to the formation of a trench or fold mountains. iii. Transform plate boundary, which involves sliding of the tectonic plates past each other, leading to the formation of an undersea canyon or linear fault valley. 6. In addition to the 3 plate boundaries you listed above, there is one more major tectonic setting we discussed in lecture. What is it, and what kind of movement occurs there? Mantle plumes, which involve the continued movement of tectonic plate that leads to the formation of a series of islands. 7. In which of the 4 tectonic settings that you listed in Questions 5 and 6 do volcanoes occur? Volcanoes occur in the Convergent plate setting. 8. Is the mantle solid or liquid? The mantle consists of a solid rock. 9. There are 3 ways the mantle can melt. What are they? i. The mantle can melt due to a rise in temperature. ii. The mantle can melt due to a decrease in pressure. iii. The mantle can melt due a change in chemical composition. 10. How is magma generated at hotspots? The rock material that makeup the mantle melts due to a rise in temperature thereby generating basaltic magma. 11. How is magma generated at mid-ocean ridges? The rock material that makeup the mantle melts due to decompression thereby generating basaltic magma, which will erupt as sheet flows or pillow basalts and form gabbros, intrusive dikes, and sills (Gill, 2009). 12. How is magma generated at subduction zones? The melting of the rock material takes place by fluxing the mantle with water, leading to changes in chemical composition. 13. What is viscosity? Give a brief definition, and a few examples of lava types with different viscosities. Viscosity refers to the ability of lava to resist flow. i. Pahoehoe is the lava with the lowest viscosity thereby flowing quickly and forming thin flows. ii. Aa is the lava with a high viscosity thereby moving slowly and forming thick flows. iii. Block the lava that has extremely high viscosity thereby forming blocky flows. 14. How does the viscosity of lava determine the shape of the volcano? Lava with low viscosity forms a shield mountain, which is low-lying because it flows over a long distance. On the other hand the lava with high viscosity forms a dome-shaped mountain because it flows over a short distance before solidification (Gill, 2009). 15. Describe at least two different types of volcanoes based on shape. i. Shield volcanoes, which are flat and low with small and flowing eruptions. Shield volcano ii. Conic volcanoes, which are largest and tallest volcanoes with explosive eruptions. Conic volcano 16. How is silica content used to classify different types of volcanic rocks? As part of your explanation, give some examples of volcanic rocks with different silica contents. i. Oversaturated igneous rocks, such as rhyolite, have high silica content. ii. Undersaturated igneous rocks, such as ijolite, are silica deficient. 17. How does silica content affect the viscosity of magma and lava? High silica content leads to the formation of a magma and lava that is more viscous than when the silica content is low. The viscosity is high because of the strong bonds between silica and oxygen. 18. What is the most important control on the eruption style of volcanoes? Viscosity and gas content of magma control the eruptive style of volcanoes. 19. Are explosive eruptions characterized by lots of gas, or little gas? Lots of gas. 20. Are effusive eruptions characterized by lots of gas, or little gas? Little gas. 21. What are intrusive igneous rocks? Define them, and give an example of an intrusive igneous rock. Intrusive igneous rocks refer to the igneous rocks that form when magma crystallizes within the Earth’s crust. Granite is the common example of intrusive igneous rocks. 22. What are extrusive igneous rocks? Define them, and give an example of an extrusive igneous rock with the same chemical composition as the rock you listed in Question 20. Extrusive igneous rocks refer to the igneous rocks that form when magma crystallizes on the Earth’s surface (Gill, 2009). Basalt is the common example of extrusive igneous rocks. 23. Think about the Cascade volcanoes. Where in the Cascades are intrusive igneous rocks forming? Intrusive igneous rocks form within the vents before the magma moves to the Earth’s surface. 24. Where in the Cascades are extrusive igneous rocks forming? Extrusive igneous rocks form on the surface of Cascades and at the foot of the Cascade Mountains. 25. What is a pyroclastic flow? Is it explosive or effusive? Give an example of a volcanic eruption that produced pyroclastic flows. A pyroclastic flow refers to a fast-moving mass of hot rocks and gases. It is evident that a pyroclastic flow is explosive because of the fast-moving gases. The volcanic eruption from St. Augustine volcano is an example of volcano that produced a pyroclastic flow. 26. What is a lava flow? Is it explosive or effusive? Give an example of a volcanic eruption that produced lava flows. A lava flow refers the movement molten rock from a volcanic mountain at a slow speed due to the absence of hot gases (Gill, 2009). It is evident that a volcanic flow is effusive because it does not involve hot gases. The volcanic eruption from Mauna Loa volcano is an example of volcano that produced a lava flow. 27. What is a supervolcano? Give an example of a supervolcano, and specific things that are measured in order to classify volcanoes as supervolcanoes. A supervolcano refers to a volcano that can produce an eruption with a large volume of about 1000 km3. An example of a supervolcano is Yellowstone. A large volume of the lava that comes out from the vent helps in classifying volcanoes as supervolcanoes. 28. How might the eruption of Thera be related to myths about the lost city of Atlantis? The eruption of Thera is among the largest volcanic eruptions recorded. Atlantis was city that sunk into the ocean many years ago. The eruption of Thera might have caused the catastrophe. 29. How was the eruption of Mount Vesuvius in 79 A.D. similar to the 1980 eruption of Mt. St. Helens? The eruptions took place at the subduction zones. The eruptions were felsic and had high viscosity with a high content of gas and tephra. 30. Are eruptions like the ones you read about and saw in the videos likely to occur in the Cascades in the future? Provide some evidence to support your answer. Yes, they are likely to occur in the Cascades in the future. This is because the Cascade volcanoes are active. Reference Gill, M. (2009). Volcanic eruptions. Huntington Beach, Calif.: Creative Teaching Press. Read More