GEOL101Exam2ShortEssayQuestions

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California State University, Fullerton *

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Geology

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Apr 3, 2024

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Eric Nakayama Professor Loyd GEOL 101 3 October 2023 Essay 2 Responses for Eric Nakayama 1) Define mineral. Be sure to include the required characteristics that makes a material a mineral. Identify three example minerals. A mineral is a crystalline compound that is mined from the crust. What makes a material a mineral is that a mineral must be a naturally occurring, inorganic, crystalline solid with a definite chemical composition. When it comes to the term “naturally occurring,” it means that a mineral occurs in nature but not made by humans. An inorganic mineral is a mineral that cannot contain compounds composed of organic carbon that is found in all living things. A crystalline solid is where atoms in minerals are arranged in an orderly fashion to create a crystalline structure. A chemical composition is “definite, but sometimes variable” in a mineral where elements can be present in any combination. There are three examples for each type of characteristics that make a material a mineral. Halite (table salt) is one example of a naturally occurring mineral. Calcite (in a form of calcium carbonate) is one example of an inorganic mineral. Quartz (containing silicon and oxygen) is one example of a crystalline solid mineral. 2) Describe the difference between intrusive and extrusive igneous rocks. How can geologists tell the difference between using textural indicators? Describe why these textural differences form. Provide an example of an intrusive and extrusive igneous rock.

There is a difference between intrusive and extrusive igneous rocks. Intrusive igneous rocks crystallize in the subsurface of Earth while extrusive ones crystallize on the Earth’s surface. There is a difference that geologists can tell between those types of igneous rocks using textural indicators. Geologists can find extrusive igneous rocks that have aphanitic, vesicular, glassy, or pyroclastic textures because extrusive igneous rocks are erupted onto the surface and cool quickly, leading to fine-grained texture. Geologists can find intrusive igneous rocks that have either phaneritic, porphyritic, or pegmatitic textures because intrusive igneous rocks solidify at depth and cool slowly, leading to coarse-grained texture. One example of an intrusive igneous rock is granite, and one example of an extrusive igneous rock is andesite. 3) Describe the differences between shield and stratovolcanoes. Discuss viscosity, silica contents, temperatures and explosivity differences. Include an example of where each type of volcano occurs on Earth. There are differences between shield and stratovolcanoes. Shield volcanoes are fed by low-silica, low-gas magmas that produce basaltic lava in the form of pahoehoe and aa flows which are fluid and rarely explosive. Basaltic lavas in shield volcanoes maintain a higher temperature, but they cannot hold a steep slope, due to low viscosity. Stratovolcanoes, or composite volcanoes, consist of alternating andesitic lava flows and layers of explosively ejected pyroclastic deposits. Due to high viscosity and low temperature, andesitic lava is difficult to erupt. The result is explosive eruptions due to the buildup of gases within the magma. These eruptions in stratovolcanoes produce layers of silica-rich lava and ash. One example of a shield volcano that occurs is on Mauna Loa, Hawaii. One example of a stratovolcano that occurs is on Mount Fuji, Japan.

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