Geology 111 Chapters 1-4 Notes
Geology 111 Chapters 1-4 Notes 111
University of Louisiana at Lafayette
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Popular in Geology
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This 10 page Study Guide was uploaded by Maria Luisa Cepeda on Friday February 5, 2016. The Study Guide belongs to 111 at University of Louisiana at Lafayette taught by Dr. Duex in Spring 2016. Since its upload, it has received 64 views. For similar materials see Geology in Geology at University of Louisiana at Lafayette.
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Date Created: 02/05/16
Chapter 1 Physical Geology- materials and processes within and on Earth’s surface Geologic Time o Earth4.6 billion years old o Oldest rocks about 4 billion years old o Oldest fossils about the same o Humansbeen around 2 million years 0.043% of Earth’s history o Multi celled organismsaround for 700 million years15% of E.H More than 1,800 planets have been discovered outside the Solar System Scientific Method: observerecordhypothesizetesttheory o How Q’s are answered o Observation o Record it o Hypothesis (possible explanation) o Test itexperiment or more observations o Scientific theory: if hypothesis survives repeated testing Geology and Theories o Uniformitarianism: Processes on Earth today = those in past o James Hutton- “The present is the key to the past” o Natural laws don’t change but rates and intensity of processes may vary o For every natural phenomenonnatural explanation o Some geologic events are rapid (meteor crater), others are slow o Seafloor spreading: Atlantic Ocean is expanding Natural World: what we know o The universe Galaxies: clusters of stars Stars: luminous bodies, H, He, fusion Solar systems Sun and planets, moons, asteroids, meteorites, comets, dust. Planets: 8 major, dwarfs (many) Earth: accretion, differentiation=layers What we can’t seedark matter o The origin of the universe “Big Bang” Theory: universe originated 13-14 million years ago Based on Einstein’s theory of relativity E=mc^2 Diamonds1 of first minerals that formed Rate of expansion of universe is increasing Afterglow of Big Bang: 2.7 K warmer Hubble Telescopegalaxies discovered NASA estimate: 125 billion galaxies The Origin of the Solar System o Solar Nebula Theory Collapse of material in spiral arm of Milky Way Concentrated material in center formed Sun Planets formed by collision & accretion o Solar Nebula Hypothesis Sun forms, planets grow by collisions, accretion (gas) o Our solar system part of Milky Way Planets of Solar System o Inner (Terrestial) planets Relatively small size, dense, “rocky” solid, thin atmospheres, few moons. o Outer (Jovian) planets Large size (Jupiter 300X Earth size, Saturn 77x lighter (less dense), frozen gases (not rocky), thick (dense) atms. Most significant event in Earth’s history o Settling of materiallayered Earth Arrangement led to the formation of continents, oceans, and atm. Heavy materialinner coreFe, Ni melt to Earth’s liquid inner core Comparing Layers of Earth o Whole Earth: Mg + Fe +O +Si heavier materials o Crust: Si + O + Al ligther materials Hard outer layer we live on Oceanic=basaltic/mafic materials (Mg + Fe; ol + px + plag) SG= 3 g/cm3, 5-10 km thick Heavier so they sink Continental: granitic/felsic (Si + Al + K/Na; Feldspars +qtz) SG= 2.7; 20- 70 km thick Lighter materials so they float o Mantle: solid, ultra matic, ductile/plastic, surrounds the core 3 distinct zones, SG= 3.3-5.7;depth: 2990 km o Core: Fe & Ni; very dense Outer coreliquid Inner core solid The 2 create an active magnetic field (moon and mars lost the active mag. Field) Chapter 2: Plate Tectonics The Unifying Theory; Discovery, Synthesis, Boundaries & 3 Movement; Pangaea; Mantle Convection; the Scientific Minerals - Definition: natural, inorganic, solid, specified composition and Structure; Matter: Elements & Atoms; Bonding & Compounds; Mineral Groups: Silicates, Carbonates, & others; Mineral Properties; Common & Rock-forming Minerals; Minerals & Society: Physical Properties & Identification of Minerals. Method revisited. Plate Tectonic Theory o Explains the interactions of layers o Earth’s Lithosphere: divided into rigid plates of various sizes that move over the asthenosphere Why do plates move? o Convection cells How do plates move? 3 Types of Plate Margins o Divergent: plates move apart, seen primarily in Mid Ocean Ridges (seafloor spreading) New oceanic material forms from spreading centers. New lithosphere is created. (Plate area increases) o Convergent: plates come together or collide and one plate is recycled into the mantle, seen in active mountain belts and volcanic arcs. (Plate area decreases) o Transform faults: plates slide past one another horizontally, seen in major faults. (plate area does not change) Chapter 3: Minerals Rocks and minerals help determine the structure of the Earth Natural occurring, building blocks of rocks Inorganic Have specific crystal structures = arranged atoms Defined chemical composition Economically important Indicate environment of formation o Minerals found in volcanic rocks prove that there were eruptions that brought molten rock to Earth’s surface. o Ex: iodine salt forms Illustrate basic principles Brick/ stone, nails/ screws, door knobs/hinges Atoms combine to form Crystal Structure of Mineral o Chem elements form compounds with one another by gaining/losing electrons or sharing them (covalent bonds) Ionic bonds- attraction between positive ions and negative ions are the dominant type of chem bonds in mineral structures. o Mineral crystallizes: there is a 3D structure consisting of atoms arranged in a specific way that is repeated in all directions. Common & Rock-forming Minerals o Silicates Most abundant class of minerals in Earth’s crust Composed of Oxygen and Silicon ions (2 most abundant elements in crust) combined w/ cations of other elements. Silicates are made up of silicate ions(Si4+) that are linked in various ways. Ex: Olivine, Pyroxene, Amphibole, Mica and Feldspar 8 Minerals that Comprise Most Igneous Rocks: Felsic Minerals: light colored, lower density, no Fe or Mg. Silica-rich o Quartz (SiO4): No cleavage, conchoidal fracture o Plagioclase Feldspar: 2 clv intersecting at 90, striations. Contain variying amounts of Ca and Na. o Alkali (K) Feldspar (orthoclase): 2 clv 90 exsolution lamealle. Contain Potassium K. o Difference between feldspars? – chemical composition. o Muscovite mica: 1 clv plane, light color Mafic Minerals: dark colored, higher density, Fe and Mg present o Biotite mica: 1 clv, black o Amphiboles (hornblende): 2 clv at 60 and 120 o Pyroxene: 2 clv planes at 90 o Olivine: green/ dark o Carbonates Minerals composed of carbonate ions (CO3 2-) bonded to calcium, magnesium or both. Ex: Calcite o Oxides Made up of Oxygen (O2-) and cations (metallic elements). Ex: Hematite (iron oxide Fe2O3) o Sulfides Compounds of sulfide anion (S2-) + cations Ex: Pyrite (iron sulfide) o Sulfates Sulfate anion (SO4 2-) + cations Ex: Anhydrite (calcium sulfate CaSO4 How are minerals identified? -Internal structure and chemical composition -Most properties are constant - Physical properties Hardness “Relative scratchability”- how easy it is to scratch a mineral’s surface. Internal structure and strength of bonds Based on Moh’s Scale from 1 to 10 Hard Minerals will scratch glass and cannot be scratched w/ knife or nail. o Strong chem bondshard minerals o Covalent bonded minerals are harder than ionically bonded ones. Soft Minerals will not scratch glass and can be scratched w/ knife or nail. Color: may not be diagnostic, influenced by impurities, chem formula. Crystal form: reflects internal geometry and composition. Perfect crystals are rare may be useful in identification Cleavage: Tendency to split along planar surfaces Mineral breaks along planes that have weak bonds. The way a mineral breaks, diff. patterns. Poor cleavif cystal structure bonds are strong (Covalent) Good cleav when bonds are weak (ionic bonds) Fracture: mineral breaks along irregular surfaces when no weak planes exist. Jagged edges Pure quarts tends to fracture along smoothly curved surfaces called conchoidal fractures Ex: micaexcellent cleavage because of weak bonds in one planar direction. Luster: the way mineral reflects light. It varies in intensity from bright to dull. Metallic luster: strong reflections on opaque surfaces w/ a silvery, gold, brassy, or coppery sheen. o Hardness, Magnetic? Tenacity (tendency to break) Nonmentallic luster: vitreous (bright as in glass), waxy, pearly, earthy, greasy, porcelaneous. Streak: color of fine powder of a substance after it has been scratched A mineral’s streak usually same among all the mineral’s varieties. More diagnostic than color Reaction to Acid Carbonate minerals will give off bubbles when HCl is applied. Striations Straight hairline grooves on the cleavage surfaces of some minerals. (exsolution lameallae) How doe we do it more precisely/ scientifically? o Thin sections o X Ray diffraction o Chemical analysis Mineral form o Important minerals Pyroxene: 90 degree cleavage direction Amphibole: 60 degree and 120 degree Chapter 4: Rocks Rocks- aggregates of minerals, a few are composed of nonmineral matter Noncrystal rock types: glassy volcanic rocks + pumice; coal- made up of plant remains. Magma- liquid molten rock forms at places in lower crust and mantle where temps are high enough for partial rock melting. -Minerals crystallize at different temps Igneous Rocks: formed by crystallization (solidification) of molten rock (magma) (Ex: basalt and granite) o Most of the minerals of igneous rocks silicates Abundant in Earth’s crust + melt at high temps and pressures reached in deeper parts of crust and in mantle. The most commonly found silicate minerals are quartz, feldspars, micas, pyroxenes, amphiboles, and olivines. How are igneous rocks identified? o Field Relations: what rock looks like in its natural setting ExtrusiveVolcanic Extrusive ign. Rocks form when lava erupts at surface and cools rapidly. Ex: basalt rocks recognized byglassy or fine-grained texture. IntrusivePlutonic Form when magma intrudes into unmelted rock deep in Earth’s crust and cools slowly. Intrusive ign. Rocks cool slowly in Earth’s interior, have large crystals. This producescoarse-grained rocks like granite. o Texture: sizes and shapes of a rock’s mineral crystals or grains and the way they are put together. (Mineral grain size) Why is it significant? texture indicates rate + place of cooling Glassy (no crystal) Volcanic Coarse-grained (Phaneritic): grains easily visible. Enough time grow larger crystals, slow crystallization. Fine-grained(Aphanitic): grains not large enough to be seen. For ex: when there’s an eruption lava cools and solidifies rapidly so crystals don’t have as much time to grow. o MineralogyChemical Composition: relative proportions of a rock’s minerals. FELSIC Rocks (Feldspar- Silica): Fe + Mg poor light color ; Silica rich Refers to feldspars and silica-rich materials. Quartz, Feldspar, Mica. Ex: Granite rock (intrusive); Rhyolite (extrusive equiv of granite)both are felsic, but differ in texture Intermediate Gray/ speckled (color patches) Feldspar, Quartz, Mica, Amphibole Diorite- intrusive, coarse-grained Andesite- extrusive, fine-grained MAFIC Rocks( Magnesium-Ferric): Fe + Mg rich dark color ; Silica poor Contain a lot of pyroxenes and olivines Poor in silica but rich in Fe and Mg Gabbro is coarse-grained intrusive/phaneritic ign rock, has abundance of mafic minerals especially pyroxenes. Basalt- extrusive/aphanitic, most abundant igneous rock of the crust, it is found underneath seafloor. Ultramafic Very dark, often green Olivine rich, poor in silica Peridotite rock (intrusive) Bowen’s Reaction Series o Order of crystallization of magma
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