GEOL 1100 Exam 1 Study Guide - Hawkins
GEOL 1100 Exam 1 Study Guide - Hawkins GEOL 1100 - 002
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This 4 page Study Guide was uploaded by Hannah Rowlett on Saturday February 6, 2016. The Study Guide belongs to GEOL 1100 - 002 at Auburn University taught by John F Hawkins in Fall 2015. Since its upload, it has received 91 views. For similar materials see Dynamic Earth in Geology at Auburn University.
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Date Created: 02/06/16
GEOL 1100 – Test 1 Study Guide – Hawkins Lithosphere: earth’s layers; inner, outer, mantle, crust o Crust Inorganic, thin, solid, brittle, rigid, cool Continental crust: Low density Felsic: SiO2rich. Silica, aluminum, oxygen White, pink, light colors Oceanic crust: Higher density Mafic: Iron, magnesium, calcium Green, black, deep, dark colors MINERALS How To Be a Mineral 1. SOLID: even if a mineral is melted down, it is no longer considered a mineral 2. INORGANIC: not living; not made of organic compounds 3. NATURAL: must occur in nature FIRST and not in a lab; however a lab created quartz is still a mineral because it does occur naturally 4. SPECIFIC CHEMICAL COMPOSITION: always the same (H O) 2 5. CYSTAL-LIKE PATTERNS: mineral always has this structure – if its structure changes it becomes a different mineral Ice is a mineral! 8 Elements in Minerals o silicon silicate minerals have these elements o oxygen o aluminum o magnesium o iron o sodium o potassium o calcium Tetrahedrals o Tetrahedral base for all silicates o Silica tetrahedral has 1 silica and 4 oxygens Negative 4 charge In order to balance the negative charge and make it neutral, must add positively charged elements Fe +2; Mg +2; Al +3; K +1; Na +1; Ca +2 1400 C Bowens ReaK-Feldspar Muscovite Mafic Series Quartz Pyroxene – single continuous Calcium-rich Felsic 800 C Olivinechainttpforoldiscontinuouset Sodium-rich Plagioclase Bowen’s Reaction Series o Lava cools, forms mafic minerals o As temp drops, there is less energy, which means more bonding occurs o The discontinuous side changes structures when cooling, changing its minerals This side uses iron and magnesium to satisfy the negative charge o When all of Fe and Mg is used, Aluminum and Potassium are next K-Feldspar Muscovite o Quartz uses just Silica and Oxygen – SiO 2 o The continuous side uses Calcium and Sodium – molecules are too large to hold with just one tetrahedral – becomes 2 tetrahedrals (Si 2 8 – charge is now -8 Continuous because structure remains same – still plagioclase Mineral Properties o Luster – reflected light Metallic, dull/earthy, sub-metallic Unreliable; need fresh surface o Hardness Moh’s Scale of Hardness 1-10 Talc 1, Diamond 10 o Cleavage – breaks along planes; mineral should have one or more flat surfaces Weak bonding yields planar cleavage Single, double chain o Fracture – breaks in pieces 3-D framework o Crystal form or habit – how crystal will grow if there is room to grow o Color – often unreliable; ex: quartz o Streak – color of a mineral in its powdered form Nullify impurities Accurate color Less variable ROCKS 3 Types Igneous Sedimentary Metamorphic Igneous Rocks Solidifies from molten materials Intrusive and extrusive rocks Intrusive Rocks Crystallization of magma – cooled inside earth’s surface Cool at different rates o Phaneritic texture – large crystals visible to the naked eye Cools slowly because they are deeper in the earth and therefore hotter Slower it cools, the more time the crystals have to grow Can see color variations in rock o Aphanitic texture – fine grain texture – crystals not visible Cools faster than phaneritic Intrudes closer to earth’s surface – more shallow Crystals have less time to grow o Porphyritic texture – mixing of textures Mixed cooling rates Combination of phaneritic and aphanitic texture Extrusive Rocks cool above the surface volcanic rocks glassy texture – rapid cooling – no time for crystals to form o obsidian – occurs when lava is ejected from volcano vesicular – fast cooling o pressure drops, gases expand and escape creating holes in rock o examples pumice – felsic scoria – mafic pyroclastic o occur when smaller fragments of rock explode from volcano and weld together o known as tuff or welded tuff Viscosity is the resistance to flow high viscosity = more resistance; thicker silica is the controlling factor in viscosity in regards to Bowens Reaction Series, silica increases as you travel down o low silica = low viscosity – Mafic is less viscous o high silica = high viscosity – Felsic is more viscous Intrusive Rock Bodies cut through existing rock Plutons: melt their way through crust and cools at surface – cools slowly – phaneritic texture o Batholiths: huge – surface exposure over 100 km; ex: Yosemite o Laccoliths: smaller – ex: Stone Mountain o Dikes: shallow intrusions with aphanitic texture cut across layers of rock cool quickly could be felsic or mafic o Sills: run parallel to layers of current rock; “sills fill” Dikes are always the source of sills o Volcanic Neck: shallow intrusions that form when magma solidifies in throat of volcano was inside of the volcano, but volcano eroded columnar jointing: magma cools and forms grooves on sides cools slowly, contracts, creates a polygonal feature varies in sides – 3-7 o Xenolith: rock fragment incased by intrusive rock Older than surrounding rock
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