08/26/2018 SmartFigure 3.1 The Rock Cycle Earth Science 15th Edition Chapter 3 Rocks: Materials of the Solid Earth Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Learning Objectives • • • • • Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Alternate Paths 3.1 Sketch, label, and explain the rock cycle. 3.2 Describe the two criteria used to classify igneous rocks and explain how the rate of cooling influences the crystal size of minerals. 3.3 List and describe the different categories of sedimentary rocks and discuss the processes that change sediment into sedimentary rock. 3.4 Define metamorphism, explain how metamorphic rocks form, and describe the agents of metamorphism. • Full cycle does not always take place due to “shortcuts” or interruptions – e.g., Sedimentary rock melts – e.g., Igneous rock is metamorphosed – e.g., Sedimentary rock is weathered – e.g., Metamorphic rock is weathered 3.5 Distinguish between metallic and nonmetallic mineral resources and list at least two examples of each. Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved 3.1 Earth as a System: The Rock Cycle 3.2 Igneous Rocks: “Formed by Fire” Sketch, label, and explain the rock cycle. Describe the two criteria used to classify igneous rocks and explain how the rate of cooling influences the crystal size of minerals. • The Basic Cycle – Magma: Crystallization above or below ground to form igneous rock – Weathering: Breakdown of a material at the Earth’s surface – Sediment: Solid particles produced through weathering – Lithification: Conversion of sediments through compaction and crystallization by groundwater to form sedimentary rock – Metamorphism: Change due to high temperatures and pressures below ground to form metamorphic rock Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved • Form as magma cools and crystallizes – Rocks formed inside Earth are called plutonic or intrusive rocks – Rocks formed on the surface ▪ Formed from lava (a material similar to magma, but without gas ▪ Called volcanic or extrusive rocks Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved 1 08/26/2018 From Magma to Crystalline Rock • Composed of ions of silicate minerals – Ions are arranged into orderly patterns during cooling – Crystal size is determined by the rate of cooling ▪ Slow rate forms large crystals ▪ Fast rate forms microscopic crystals ▪ Very fast rate forms glass What Can Igneous Textures Tell Us? • Texture: size, shape, and arrangement of minerals that make up rock – Fine-grained—fast rate of cooling – Coarse-grained—slow rate of cooling – Porphyritic (two crystal sizes)—two rates of cooling – Glassy—very fast rate of cooling – Vesicular—contains hole left by gas bubbles – Pyroclastic—fragmented; produced by consolidation of volcanic fragments Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Igneous Compositions Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved SmartFigure 3.5 Igneous Rock Textures • Mainly composed of silicate minerals – Granitic (Felsic) Compositions ▪ Richer in light silicates – Basaltic (Mafic) Compositions ▪ Richer in dark silicates Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved SmartFigure 3.4 Composition of Common Igneous Rocks Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Common Igneous Rocks • Granitic Rocks – Felsic: composed of light-colored silicates—quartz and feldspar – Common: granite, rhyolite, obsidian • Andesitic (Intermediate) Rocks – Mixture of felsic and mafic compositions – Common: andesite, diorite • Basaltic Rocks – Mafic: composed of dark-colored silicates – Common: basalt, gabbro Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved 2 08/26/2018 SmartFigure 3.8 Classification of Igneous Rocks, Based on Their Mineral Composition and Texture 3.3 Sedimentary Rocks: Compacted and Cemented Sediment List and describe the different categories of sedimentary rocks and discuss the processes that change sediment into sedimentary rock. • Form from sediment (weathered products) • About 75 percent of all rock outcrops on the continents • Used to reconstruct much of Earth’s history – Clues to past environments – Provide information about sediment transport – Rocks often contain fossils Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved How Igneous Rocks Form • Explained by Bowen’s reaction series, which shows the order of mineral crystallization • Influenced by crystal settling in the magma Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Figure 3.13 Bowen’s Reaction Series Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Types of Sedimentary Rocks • Detrital – Solid particles from weathering – Classified by particle size and shape – Common: conglomerate, breccia, sandstone, siltstone, shale Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Figure 3.16 Detrital Sedimentary Rocks Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved 3 08/26/2018 Figure 3.17 Chemical, Biochemical, and Organic Sedimentary Rocks Sedimentary Rocks • Sedimentary rocks are produced through lithification – Loose sediments are transformed into solid rock – Lithification processes • Compaction • Cementation by – Calcite – Silica – Iron Oxide Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Types of Sedimentary Rocks © 2015 Pearson Education, Inc. Sedimentary Rocks • Features of sedimentary rocks • Chemical, Biochemical, and Organic – Derived from ions carried in solution to lakes and seas – Classified by composition – Common: limestone, gypsum, chert, coal Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Lithification of Sediment Figure 3.23 Compaction and Cementation • Lithification: processes by which sediments are transformed into sedimentary rocks – Compaction ▪ Overlying sediment – Cementation ▪ By Calcite, Silica, and Iron Oxide Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved – Strata, or beds (most characteristic) – Bedding planes separate strata – Fossils • • • • • Traces or remains of prehistoric life Are the most important inclusions Help determine past environments Used as time indicators Used for matching rocks from different places © 2015 Pearson Education, Inc. 3.4 Metamorphic Rocks: New Rock from Old Define metamorphism, explain how metamorphic rocks form, and describe the agents of metamorphism. • Form from preexisting igneous, sedimentary, or metamorphic rocks • Take place due to temperatures and pressures unlike those in which it formed • Leads to changes in mineralogy, texture, and chemical composition Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved 4 08/26/2018 Metamorphic Rocks: New from Old • Often progresses incrementally • Degrees of metamorphism – Exhibited by rock texture and mineralogy – Low-grade, slight changes (e.g., shale becomes slate) – High-grade, obliteration of original features (e.g., shale becomes gneiss) What Drives Metamorphism? • Metamorphic agents – Heat – Pressure (stress) ▪ Confining pressure—from burial ▪ Differential stress—occurs during mountain building – Chemically active fluids ▪ Mainly water and other volatiles ▪ Promote recrystallization by enhancing ion migration Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Figure 3.27 Metamorphic Grade Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved SmartFigure 3.28 Confining Pressure and Differential Stress Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Metamorphic Rocks Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Metamorphic Textures • Metamorphic settings – Contact, or thermal, metamorphism • Occurs near a body of magma • Changes are driven by a rise in temperature – Regional metamorphism • Directed pressures and high temperatures during mountain building • Produces the greatest volume of metamorphic rock © 2015 Pearson Education, Inc. • Foliation – Flat arrangement of mineral grains or structures – Minerals are perpendicular to the compressional force – Common: slate, phyllite, schist, gneiss • Nonfoliated texture – Contain equidimensional crystals – Resembles a coarse-grained igneous rock – Common: quartzite, marble Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved 5 08/26/2018 SmartFigure 3.29 Rotation of Platy and Elongated Mineral Grains to Produce Foliated Texture Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Figure 3.30 Common Metamorphic Rocks Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved END Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved 6
