Laboratory 4 _ Volcanoes, Plutons, and Igneous Rocks_ ESS 101 B Sp 22_ Introduction To Geology And S

2022/4/29 17:45 Laboratory 4 : Volcanoes, Plutons, and Igneous Rocks: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651018 1/50 * Some questions not yet graded Laboratory 4 : Volcanoes, Plutons, and Igneous Rocks Due May 1 at 11:59pm Points 15 Questions 42 Available Apr 22 at 9am - May 1 at 11:59pm 10 days Time Limit None Allowed Attempts 2 Instructions Attempt History Attempt Time Score LATEST Attempt 1 5,515 minutes 12.83 out of 15 *  Answers will be shown after your last attempt Score for this attempt: 12.83 out of 15 * Submitted Apr 29 at 5:41pm This attempt took 5,515 minutes. The Prelab Video serves as an introduction to the topics covered in this lab. See below. Igneous Processes pre lab line here (https://youtu.be/m24UfUP60lo) (https://youtu.be/m24UfUP60lo) A PDF version of this lab can be found below: Lab4_IgneousRocks_Sum20.pdf Take the Quiz Again Learning Objectives

2022/4/29 17:45 Laboratory 4 : Volcanoes, Plutons, and Igneous Rocks: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651018 2/50 By completing this lab, students will learn how: Igneous rocks form when magma cools, either slowly underground or rapidly at earth’s surface (i.e. near volcanoes). Magma cooling processes affect the size of crystals in igneous rocks. Bigger crystals form in slow-cooling, underground magma chambers, and smaller crystals form in fast-cooling lava flows/eruptions. To recognize eight common igneous minerals, and nine common igneous rocks. Mafic rocks are usually dark-colored and felsic rocks are usually light-colored. The viscosity of lavas relates to their silica content. Felsic (or silica- rich) lavas are more viscous than mafic (or silica-poor) lavas that flow like rivers. Lava viscosity affects the shape of volcanoes. Introduction Igneous rocks form when liquid rock cools and crystallizes. Liquid rock is called magma when underground and lava when on the surface. Igneous rocks have different chemical and physical characteristics depending on what they are made out of and how or where they formed. Like using paleomagnetic stripes to understand tectonic movement, geologists can use other information recorded in igneous rocks to study earth’s history. In this lab, we will examine several different igneous rocks, and we will explore the various conditions under which they formed. Igneous rocks are classified by mineral composition and by mineral grain texture . This classification system is interpretive , because these characteristics imply something about the source of the magma and the conditions under which the rock formed. Chemical composition . The mineralogy of an igneous rock is related to the chemical composition of the cooling parent magma from which it forms. For example, a magma that is mostly Si, Fe, Mg, Al, Ca, and O, a common composition for mantle melts, is likely to form olivine, a mineral made out of Si, Fe, Mg, and O and plagioclase, a mineral made out of Si, Al, Ca, and O. The chemical ingredients in the melt turn into the minerals in the rock.

2022/4/29 17:45 Laboratory 4 : Volcanoes, Plutons, and Igneous Rocks: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651018 3/50 Texture. The sizes and arrangement of the minerals in an igneous rock is known as texture. In this case, texture is not how the rock feels but how it looks. Igneous rock texture relates to the cooling environment in which the rock formed. The same melt composition can form very different rocks depending on the cooling rate. Slow cooling inside the earth forms large (greater than about a quarter of a millimeter) crystals, which slowly, over thousands of years grow together to form intrusive, or plutonic, rocks. Volcanic eruptions result in rapid magma cooling (seconds to days), and the formation of igneous rocks with small grains (often too small to see with your eyes). During a volcanic eruption, magma does not have enough time to solidify before it reaches the surface. The rocks that form at the surface during a volcanic eruption cool rapidly and are called extrusive or volcanic rocks. A. Igneous Rock Composition 99% of the total bulk of most igneous rocks is made up of only eight elements: silicon (Si) sodium (Na) oxygen (O) aluminum (Al) magnesium (Mg) calcium (Ca) iron (Fe) potassium (K) Most of these elements occur in the crystal structures of eight minerals, which constitute over 95% of the volume of all common igneous rocks. Therefore, these minerals are of paramount importance in the study of igneous rocks. Below is a list of the common igneous rock-forming minerals, along with their diagnostic properties and chemical formulas: Mineral Properties Chemical Formula olivine Green to yellow-green; vitreous; small, (Mg,Fe) SiO 2 4

2022/4/29 17:45 Laboratory 4 : Volcanoes, Plutons, and Igneous Rocks: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651018 4/50 equidimensional grains plagioclase Usually White or Gray; 2 cleavages at 90°; elongate grains; striations Calcium Plagioclase: CaAl Si O Sodium Plagioclase: NaAlSi O pyroxene Black, greenish black, or brownish black; rather dull luster; blocky grains; poor cleavage, 2 planes at 90° Complex Ca-Mg-Fe-Al silicates amphibole Black with shiny, splintery appearance; two cleavages at 60° and 120°; elongate grains Complex hydrous Na- Ca-Mg-Fe-Al silicates biotite Shiny, black flexible sheets; one perfect cleavage K(Mg,Fe) AlSi O (OH) orthoclase Usually white or pink; 2 cleavages at 90°; equidimensional grains KAlSi O muscovite Shiny, silvery flexible sheets; one perfect cleavage KAl AlSi O (OH) quartz Colorless to gray; glassy with conchoidal fracture; irregular grains in intrusive rocks; equidimensional phenocrysts in extrusive rocks SiO Table 4-1 Eight most common minerals found in igneous rocks, their diagnostic properties, and chemical composition. Most igneous rocks can be classified into three compositional groups, based on a particular assemblage of minerals: 1. Mafic magma/lava cools to produce dark-colored (or green) rocks that are composed of dense dark (Fe-Mg rich) minerals that crystallize at high (e.g., 1000°C) temperatures. 2. Intermediate magma/lava cools to produce intermediate-color (or gray) rocks that are composed of the minerals that crystallize at mid-range (e.g., 800°C) temperatures. 3. Felsic magma cools to produce light-colored (or orange) rocks that are composed of the light-colored, lower-density (silica) minerals that crystallize at comparatively low (e.g., 600°C) temperatures. 2 2 8 3 8 3 3 10 2 3 8 3 3 10 2 2

2022/4/29 17:45 Laboratory 4 : Volcanoes, Plutons, and Igneous Rocks: ESS 101 B Sp 22: Introduction To Geology And Societal Impacts https://canvas.uw.edu/courses/1545896/quizzes/1651018 5/50 You used the following tables to identify common minerals in Lab 3. You'll need them again to identify minerals in this lab. Metallic Minerals Table A-1 Non-metallic Minerals Light Colored Minerals Table A-2 Dark Colored Minerals Table A-3 0.25 / 0.25 pts Question 1 Laboratory Honor Statement Cheating or plagiarism of any kind will not be tolerated in ESS 101. This includes copying answers from a friend or classmate, copying answers verbatim found on the internet or other literary sources, or copying any work that may answer the question being asked. Make sure you always use your own words when answering the questions in the homework and cite appropriate references if you use them to help you answer the question. Anyone caught violating the academic code of conduct (https://www.washington.edu/cssc/for-students/academic- misconduct/) will be reported to the UW Academic Misconduct representative. I acknowledge that I have carefully read and understand the above statement regarding the consequences of cheating and plagiarism, and promise to complete my work in this class with honesty and integrity. Answer "True" below supporting your acknowledgement. True False