EAR 110 1st Edition Lecture 9Outline of Last LectureI. Understanding the Periodic TableII. Major Classes of Rock forming mineralsIII. Silicate mineralsIV. Nonsilicate mineralsV. Minerals in different parts of the earthVI. Model of an atomVII. Different kinds of bondsVIII. Properties of Water MoleculesOutline of Current LectureI. IntroductionII. Textures of Igneous RocksIII. Where different textures formo Classifying Igneous Rocks1. How Igneous Rocks form2. Processes that affect composition of igneous rocks3. Viscosity of Lava4. Ways Magma CoolsCurrent LectureChapter 5: Igneous RocksI. Introduction1. Observe features of Northern New Mexico: diverse composition and texture1. Valles caldera – light colored ash2. Volcanic field with smaller volcanoes and dark lava flows3. Active rifts – Rio Grande River4. Harding Pegmatite – huge crystalsII. Textures of Igneous Rocksa. Crystalsi. (largest)pegmatite àcoarse grained àmedium grained àfine grained(smallest)ii. Slowest cooling = largest crystals; fastest cooling = smallest crystalsb. No crystalsi. Glassyii. Vesiculariii. WeldedIII. Where different textures form1. Eruption of lava – glassy, vesicular2. Rapid cooling at shallow depth – fine grainedThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.3. Slower cooling at depth – larger grains4. Water rich magma – pegmatite5. Column of volcanic ash6. Pyroclastic flowso Classifying Igneous Rocksa. Color indicates compositioni. Felsic rocks = light color: >65% silica1. Example: granite rhyoliteii. Intermediate rocks: 55-65% silica1. Example: diorite, andesiteiii. Mafic rocks = dark colored: 45-55% silica1. Example: gabbro, basaltiv. Ultramafic = very dark colored: <45% silica1. Example: pendotiteII. How Igneous Rocks forma. Melting rocksi. pressure tends to hold lattice together, increasing temperature vibrates atoms and can break bondsii. adding water lowers melting temp of rocksiii. Phase Diagrams1. Moving from a solid to a liquid is a combination of changes in pressure and temperature2. Figure in text:a. AàC is heating with burialb. CàB decompression (release of pressure)b. Processi. Partial melting at source1. Role of source area: source has strong control on composition of liquida. Example: melting of mantle creates mafic magmaii. Accumulates into rising magma bodyiii. Forms magma chamber (solidifies or rises)iv. Erupt as lava or ashIII. Processes that affect composition of igneous rocksa. Crystallization and crystal settling (floating and sinking of crystals)b. Magma mixing – two magma chambers mixingc. Assimilation – incorporation of host rocks into magmaIV. Viscosity of Lavaa. Definition: resistance to flowb. High viscosity = lava piles up, lower temp and abundant silica chainsi. *Dangerous eruptions!c. Low viscosity = lava spreads out, higher temp and few silica chainsV. Ways Magma Coolsa. Conduction into wall rocksb. Lose heat to air, water, or underlying rocksc. Interaction with hydrologic cycle – circulating water keeps wall rocks