Dynamic Earth Ch. 2 & 3 notes
Dynamic Earth Ch. 2 & 3 notes GEOL 1100 - 001
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This 5 page Class Notes was uploaded by Margaret Notetaker on Friday September 4, 2015. The Class Notes belongs to GEOL 1100 - 001 at Auburn University taught by John F Hawkins in Fall 2015. Since its upload, it has received 157 views. For similar materials see Dynamic Earth in Geology at Auburn University.
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Date Created: 09/04/15
Rock CHAPTER 2 ROCKS amp MINERALS Collection of minerals Mineral Solid inorganic natural speci c chemical composition crystallike pattern Muscovite amp Biotite Aluminum and Magnesium alters the color Felsic lighter amp Ma c darker The Important 8 Silicon Si charge of 4 Oxygen O charge of 2 Aluminum Al charge of 3 Magnesium Mg charge of 2 Iron Fe charge of 2 Sodium Na charge of 1 Potassium K charge of 1 Calcium Ca charge of 2 Silicate Minerals Formation of Silicates They form inside a magma pocket in a volcano All 8 minerals are found in the magma pocket There are high levels of Silicon and Oxygen Tetrahedral Silicate forms 4 Oxygen 1 Silicon 0 Has a charge of 4 0 Has to substitute or add other elements to neutralize charge 0 Elements that are added depends on the temperature As the temperature drops the magma cools Cooling helps the bonds stabilize and form new minerals Magnesium Iron Calcium are the rst to bond with the tetrahedral silicates Magnesium andor Iron combining with silicate tetrahedral makes olivine o All is green with olivine 0 Mg FC2SlO4 Bowen s Reaction Series 0 Olivine gt Pyroxene gt Amphibole gt Biotite Main Groups 1 Silicates a Rock forming minerals b Cations bonded to Silicon and Oxygen c Most minerals are found Within Earth s crust 2 NonSilicates a Not rock forming minerals b Oxides 0239 i Used as an abrasive CHAPTER 2 ROCKS amp MINERALS ii Rubies amp Sapphires iii Real world example is Red Mountain in Birmingham c Sul des sz39 i Pyrite galena sphalerite chalcopyrite ii Usually just an element bonded to sulfur d Carbonate CO3 i Dolomite amp calcite ii Elements bonded to carbonate ionic group e Sulfates S04 i Gypsum drywall f Halides i Elements bonded to uoride F39 chloride Cl39 hydroxide OH39 ii Salty to the taste g Phosphates P04 i Elements bonded to a phosphate ionic group ii Most common found is teeth 1 Apatite CaPO43 F Cl OH 2 Want CaPO43F because uoride is good for the teeth 3 Ionic substitutions a Ions with similar charges and sizes can be substituted in a crystal structure b Charges and sizes have to match to switch Properties Luster 0 Appearance of re ected light 0 Outward appearance can change from exposure Hardness o Moh s Hardness Scale 0 High numbers cut lower numbers Cleavage o Breaks along a straight plane 0 Pyroxene 90 0 Amphibole 120 and 60 0 Basal cleavage I Sheet silicate peels off because has weak bonds Fracture 0 Does not break evenly no planes 0 Habit how the crystal will grow if given room Color 0 Unreliable to determine mineral 0 Way mineral interacts with light 0 Use to determine trace elements Streak 0 Color of mineral in its powdered form 0 Rub mineral on porcelain plate 0 Use to distinguish between minerals with metallic luster Striation CHAPTER 2 ROCKS amp MINERALS 0 Straight parallel lines on multiple cleavage planes 0 Commonly found on Plagioclase amp Feldspar Magnetism Double Refraction 0 Light is split amp refracted into two different images Density mass volume Speci c Mass mass of substance equal volume water Taste amp Odor Color amp Density 0 Ferromagnesian Silicates Maf1c with Fe and Mg More dense Olivine high temperature low silica Pyroxene high temperature low silica Amphibole moderate temperature high silica Garnet common metamorphic mineral Mica biotite moderate temperature high silica o Nonferromagnesian Silicates Felsic Mica muscovite moderate temperature high silica Feldspars plagioclase most common mineral in crust form over a Wide range of temperatures and melt compositions Quartz low temperature high silica extremely stable at surface tends to be a major component in sedimentary rocks Clay different types in different soils 0 Polymorphism Same chemical composition but different crystal structure EX diamond and graphite Both pure carbon but physically different CHAPTER 3 ROCK CYCLE 3 Types of Rocks Igneous cooled from magma Sedimentary bits of other rocks Metamorphic heat amp pressure change rocks Igneous Crystallization of magma intrusive or lava extrusive Crystallization pathway predicts types of minerals Always follows the Bowen s Reaction Cycle Intrusive Rocks 0000 Magma below the surface The closer to the surface the faster it cools Rate of cooling depends on depth Rate of cooling in uences size of crystal I Slower cooling larger crystals I Faster cooling smaller crystals Phaneritic I Can distinguish different crystals with the naked eye I Crystals must be uniform in size I Usually found deeper beneath the surface Aphanitic I Cannot distinguish individual crystals I Magma cools too fast to grow crystals I Magma is closer to surface Porphyritic I Can distinguish some crystals I Usually found between Aphanitic amp Phaneritic Extrusive Rocks 0 O O O O Lava above the surface Obsidian I Volcanic glass I Lava cools extremely fast I Will have fracture because of fast cooling I Crystal lattice does not have time to form Vesicular I Pressure drops so quickly that gases are escaping as its cooling I Full of tiny holes from gas escaping I Has low speci c gravity probably can oat I Pumice felsic I Scoria mafic Pyroclastic Tuff I Smaller pieces of rocks are blasted from a volcano and weld together Lava Viscosity I High viscosity means it resists ow I More silica makes the lava more viscous I Felsic usually has a higher viscosity than mafic rocks CHAPTER 3 ROCK CYCLE Igneous Bodies Plutons Common Examples Stone Mountain GA Mt Rushmore Yosemite National Park Intrusive Rock Bodies Named for size shape amp relation to country rock Deep intrusions are called Plutons They crystallize slowly underground Batholith O O Deepest intrusion deeper than 100 km2 Mt Rushmore amp Yosemite National Park Laccolith o o Dike o o Sill o 0 Exposure is less than 100 km2 Stone Mountain GA Cuts vertically across the rock Usually about 2 km below the surface Fill in the rock horizontally Make layers in the rock Volcanic Neck 0 O O 0 Shallow intrusion from when magma solidi es in the throat of the volcano Magma gets trapped halfway and is revealed by erosion Popular place to build castles Devil s Tower I Famous example of columnar jointing I Magma cools and contracts very quickly I Can have 37 sides polygon shaped I Center cools and pulls materials in Xenolith O 0 Rock trapped inside a different rock Rock crystallizes in the magma chamber then the magma crystallizes around it