2/3-2/5 In class
2/3-2/5 In class GEO 101
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Popular in Geology
This 17 page Class Notes was uploaded by Cassandra Flores on Friday February 6, 2015. The Class Notes belongs to GEO 101 at University of Alabama - Tuscaloosa taught by Keene in Spring2015. Since its upload, it has received 56 views. For similar materials see Dynamic Earth in Geology at University of Alabama - Tuscaloosa.
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Date Created: 02/06/15
23 In Class Notes Thursday February 5 2015 519 PM Igneous Rocks Igneous Rock Formation What we will cover Magma formation composition and flow Igneous rocks characteristics Tectonic areas where they are found Sidenote for Finals How do scientists get money for grants Peer review evaluates for grant approval often based on design quality How do we identify minerals 1 Color 0 Can vary due to impurities quartz is great example of this 0 Least reliable method ofmineral ID 2 Streak 0 Color in powdered form I Powdering reduces impurities 3 Luster 0 Way mineral scatters light 0 2 main categories I Metallic l klnn mpfnllir of experiment Hardness O Determines strength ofchemical bonds I Moh39s hardness scale El Organizes minerals in order of their hardness on a num Specific Gravity 0 Measures density 0 Often not done exactly but by comparison in the field I Is the mineral heavierlighter than it looks Crystal Form or habit in text book 0 Shape if left alone to grow I NOT the same as cleavage or crystal structure Fracture amp Cleavage O Cleavage tendency to break along weak bonding planes I Flat shiny surfaces where rest of rock is not flatshiny O Fracture Planes are all of equal strength I Conchoidal fracture like glass Special Properties 0 Magnetism 0 Reaction to Hcl acid 0 Taste DO NOTTASTE THE ROCKS O Smell Mineral Groups Minerals grouped by chemical similarities Silicates are the most common SiO4439 Silicates Mafic O Simpler structure eric scale V IVIUIC UCIIDC UCII KLUIUICU I Because they contain Iron and Magnesium Felsic 0 More complex structure 0 Less dense light colored I Because they DO NOT contain iron or magnesium Why are minerals important 0 We use hem every day Building materials Electronics Personal products Tools drillingsanding FoodsaH OOOOO Rocks 0 Are made of minerals 3 major types of rocks 0 Igneous I From magma or lava O Sedimentary I From sediments bits of other rocks 0 Metamorphic I Changed by heat or pressure Igneous Rocks 0 quotfreezequot out of lava or magma O LAVA Melted rock outside the earth 0 MAGMA Melted rock inside the earth Where does magma come from Crust amp Upper Mantle form components for magma 0 Heat from outer core only liquid layer of earth melts this materi Magma forms in 3 ways 1 Decrease in pressure 0 Heat makes rocks melt 0 Pressure keeps rocks together 0 Same heat less pressure melt 0 Why does pressure change gt Plate tectonics plates have different weig 2 Adding volatiles 0 Volatiles evaporate easily 0 water lowers melting temperature 0 Ex Given Alcohol swabs at Dr39s office gives b sensation after the ethanol alcohol evaporate effect to rock 3 Heat transfer 0 Exactly how it sounds 0 Ex Given Baked potato melts butter by heatt Major magma types More Silica 0 Felsic Intermediate 0 Mafic Ultramafic not really covered but know that it exists Less Silica All magmas have slightly different chemical compositions gtVVhy Bowen39s Reaction Series 0 Ultramafic Solidify firstMelt last Heat ofMagma ial ghts ody immediate cold 5 Water has similar ransfer O Felsic Solidify lastMelt first i I Magmas of different temperatures rocks with different mil Magma composition is different bc Source rocks have different compositions Partial melt of source rock 0 Ex Given Chocolate chip ice cream at room temp Ice cream mel chips goes back to frozen last Assimilation Heat partially melting local rock Magma mixing Why does magma flow 0 Less dense than solid rock Squeezed by pressure 0 Ex Given What happens when you step in mud while barefoot the mud between your toes Viscosity Resistance to flow 0 Highflow slowly I Ex Given Peanut butter I Felsic magma has high viscosity 0 Lowflow quickly I Ex Given Ketchup I Mafic magma has low viscosity 0 What affects viscosity 0 Heat I More heatmore flow nerals ts before chocolate Pressure squeezes O v0IatIIes I More volatiles more flow 0 Silica content I More silica LESS flow think of sticking sand in peanut buttr spread Does molten rock only come from volcanoes O NO I Intrusive igneous rock forms without ever coming to the SUI I Extrusive igneous rock forms after reaching the surface Igneous rock Intrusive formations Magma chamber 0 Cools as pluton or batholith I Ex Pluton Stone Mountain Georgia I Ex Batholith El Capitan cliff face Magma Blister O Cools as lacolith I Ex Marcellina Mt Colorado 0 Vertical intrusion O Dyke I Ex Shiprock NM 0 Horizontal Intrusion O Sill I Ex Glacier bay Alaska Extrusive rockformations Each eruption is different er less easy to face 25 In Class Notes Thursday February 5 2015 527 PM Volcanoes Which will cool faster Depends on 0 Depth shallow faster 0 Size Smaller faster 0 Shape 0 Water more faster I Ground I Ocean Why does cooling speed matter Bowen39s reaction series o If you know minerals you can recreate eruption o Affects texture of rock Classifying Igneous Rock 0 Composition 0 Felsic intermediate mafic ultramafic Texture O Scategories 1 Aphanhk 0 Fine grain 0 Cooled quickly 0 Likely extrusive 7 Dhannrifir L I IICIIICIILID 0 Coarse grained 0 Cooled slowly ltgt Likely intrusive 3 Porphyritic 0 Large w smaller chunks of crystal 4 Glassy 0 No crystals 0 Very fast cooling 0 Vesicular ltgt Cools so fast that gasses are trapped can see quotbubblesquot gt Not all just a possibility win glassy texture 5 Pyroplastic 0 Volcanic explosion 0 Such force that surrounding rock is reduced to shards amp absorbed by lava 0 Contains pieces of broken rock Naming Igneous Rock 0 Use texture and content I Tells us about formation I Figure 415 0 Granite phaneritic felsic I Most continental crust is made of this 0 Basalt aphanitic mafic I Most oceanic crust is made ofthis In what tectonic areas are Igneous rocks formed Subduction zones 0 Continental subduction 39 I39CIDIL UL UI LUIILIIICIILCII Ll UbL 0 Island subduction I Mafic bc of oceanic crust Hot Spots O Depends on what kind of plate volcano rests on I Continental felsic I Oceanic Mafic MidOcean Ridge 0 Mafic bc you are creating oceanic floor which is primarily Basalt mafic Large igneous provinces 0 Areas created by very low viscosity mafic lava What is a volcano Vent through which molten rock reaches Earth39s surface Eventually a mountain will be built by this process but the mountain itself is a result ofvolcanic activity 0 0 Products of volcanic eruption O O O O Lava Lava Pyroplastic material Gas Geological depositsrocks 3 basic types 0 Basaltic I Most mafic I Fastest moving 0 Andesitic A I Middle range of speed IA AIELEA U KHVOIITIC I Most felsic I Slowest moving Properties determined by O Silica ontent 0 Temperature 0 Volatile content I See 23 notes for more information about this Basaltic lava O Pahoehoe I Ropey when dry 0 A39a39 I Jaggedcrumbled look 0 Pillow I Looks like pillows I Forms underwater Andesitic Lava 0 Thick flow Rhyolitic Lava O Mounds up into lava dome 0 Doesn39t really flow Types of eruptions Effusive spurting O Likely to be low viscosity basaltic lava I quotEruption of Kiaueaquot video Explosive lots of pyroplastic debris O Trapped gas explodes O Likely to be higher viscosity lava I quotMount St Helens May 18 1980quot video
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