Geology 101 Midterm 1 Study Guide
Geology 101 Midterm 1 Study Guide GEOL 101 001
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GEOL 101 001
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This 6 page Study Guide was uploaded by Madeline Wilson on Sunday January 31, 2016. The Study Guide belongs to GEOL 101 001 at University of South Carolina taught by Dr. Knapp in Spring 2016. Since its upload, it has received 105 views. For similar materials see Introduction to the Earth in Geology at University of South Carolina.
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Date Created: 01/31/16
Geology: Incorporates significant elements of all other sciences Growing national/international attention upon energy/climate/environment crises Subfields: Oceanography, ecology, geophysics, environmental geosciences, geochemistry, geobiology, volcanology, planetary science Ch 1 Modern geology – 1700s Catastrophism – Cuvier (1769-1832) – earth development – sporadic, cataclysmic events Uniformitarianism – James Hutton (1723-1779) – geologic pricesses of today worked much the same way in the past Plate techtonic “revolution,” late 1960’s early 1970’s Scientific Method Basic Assumption – natural world works in orderly fashion Objective – explain how the universe works Hypothesis – explanation offered for a set of observations Theory – hypothesis withstands many tests Scientific Model/Law – seems to be no sensible reasons to challenge Science requires: Free intellectual exchange Code of ethics References, acknowledgements “honesty, generosity, respect for evidence, openness to all ideas and opinions” (Bruce Alberts, NAS) Uniformitarianism: Natural laws do not change Slow: sediment accumulation Rapid: volcanic eruption, earthquake Geologic record: information preserved in rocks Continental crust: ~40 Km Oceanic crust: ~5Km Earth’s radius: 6,574 Km Surface rock density: 3.5 g/cm^3 whole earth: 5.5 g/cm^3 core: 8 g/cm^3 46% of crust is oxygen 44% of mantle is oxygen 85% of outer core is iron 94% of inner core is iron Plate tectonics is the only theory in earth science New ocean crust is created at mid-ocean ridges Geologic time distinguishes geology from other sciences, rate: µ/year to cm/year Large earthquakes displace within a matter of seconds 456 Billion years ago: Earth formed 542 Million years ago: Evolutionary Big Bang 420 MYA: Earliest land animals 65 MYA: disappearance of dinosaurs 5 MYA: first homonids Mt Everest – 29,000+ ft/ 8,850 meters Tectonics: greek tekton – “builer” All plate boundaries have earthquakes All-encompassing theory 12 large “lithospheric plates” (~100 Km thick) Earthquakes, volcanoes, and mountains occur at plate boundaries Interiors are stable in comparison Plates Groups of rocks all moving in the same direction Can have both oceanic and continental crust Lithosphere – the outer rigid shell of the earth (crust and uppermost mantle) (100-200 Km) Athenosphere – part of mantle beneath Litho. 200-300 Km thick, hotter, weaker Convection in mantle drives plate tectonics Plate tectonics – first proposed in 1912 by Alfred Wegener – observations of drifting sheets of ice All continents were once together as Pangea Continental Crust Oceanic Crust Weaker Stronger Thicker Thinner Lighter (~2.8 g/cm^3) Heavier (3 g/cm^3) Does not easily recycle, long lived Easily recycled, short lived Oldest: 4 billion years Oldest: ~180 million years Result of tensional forces (stresses) within crust due to upwelling mantle New lithosphere created at mid-ocean ridges Seismically active, volcanic activity Rifting caused by tensional forces The Japanese islands were formed by ocean-ocean convergence Ocean-Ocean: one plate subducts (more dense), water expelled from subducted plate is cold and rigid and generates deep earthquakes in subduction zones Island arcs: techtonic belts of high seismology, deep earthquakes in the mantle (<600 Km), active volcanoes, bordered by a submarine trench Mariana’s Trench: 35,756 ft/10,898 Km Ocean-Continent: continental crust overrides oceanic because it is lighter, continental edge crumples and is uplifted into a mountain chain roughly parallel to the deep sea trench (continental arcs), characterized by earthquakes and volcanoes Continent-continent: both continents remain afloat, Eurasian plate overrides the Indian plate, creating a much thicker crust, almost doubling it, crust crumbles and creates high mountains and a wide plateau In ocean-continent convergence is accommodated by deformation of the crust All subduction zones occur at convergent plate boundaries Transform Plate Boundaries Lithosphere is neither created not destroyed Horizontal displacement between adjacent plates Rocks of different types on each side Strong shallow earthquakes Transform faults ONLY ocean-ocean and ocean-continent have volcanoes Seafloor WWII – magnetic method to measure the local seafloor magnetic field created by magnetized rocks on the seafloor Regular patterns in the intensity of magnetic field The seafloor is a magnetic tape recorder Magnetic strips are called “isochrons” because they mark time intervals The Geodynamo System: rapid motion of the liquid outer core As the seafloor splits, ~half of the newly magnetized material moves to one side, and half of the other side Thermoremanent magnetization: when iron-reach lavas cool in the presence of earth’s magnetic field, they become slightly magnetized in the direction of the field Spreading rate (speed) = distance/time, known thanks to GPS Isochrons: boundaries between normally magnetized oceanic crust and reversely magnetized oceanic crust Oceanic crust that records negative magnetic anomalies formed when the earth’s magnetic field was reversed from what it is today Mantle Plume/Hotspot Intra plate volcanoes Formed at core – mantle boundaries starts as a build-up of heat Isotopes – different number of neutrons Mineral – naturally occurring, solid, generally inorganic, crystalline, specific chemical composition, building blocks of rocks Elements – form of matter that cannot be broken down into simpler forms, made of atoms Compounds – combinations of atoms of one or more elements in specific proportions Minerals – naturally occurring aggregates or combinations of one or more compounds Ions – atom loses/gains an electron (loses = + [cation], gains = - [anion]) Ionic bonding – opposite charge, MOST COMMON BOND (90%) Covalent – sharing of electrons in outer shell Metallic – force of attraction between valence electrons and the metal ions NaCl - sodium loses electron, chlorine gains electron, crystalline structure Covalent – electrons shared, more stable than ionic Metallic – strongest, free electron sharing Crystallization from magma – growth of a solid from gas or liquid whose constituent atoms come together Crystal growth in the solid state – if there is space Precipitation from solid – liquids evaporate from a solution ~3500 minerals, classified by anions combined with cations 90% of earth’s crust – silicates Diamond – 10 Ruby – 9 Sapphire – 9 Emerald – 8 Sodium – atomic #11, Na+: 10 electrons Diamond – covalent bonding Hardness, cleavage, fracture, luster, color, streak, crystal habit Rocks – naturally occurring aggregates or combinations of one or more minerals (marble, granite, sandstone, limestone) Lithification – recrystallization, cementation, compaction Any rock type can be turned into any other through the rock cycle Igneous – formed by solidification of magma, deep crust/upper mantle, form most of crust Intrusive – large crystals, cool slowly, inside crust, granite Extrusive – small crystals, cool rapidly, at surface, basalt Hawaiian Islands – basaltic magma Melting point of rocks – 1000 degrees Celsius (reached at a depth of 100 Km, in mantle) Increased pressure, increased melting point Increased water content lowers melting point Felsic minerals melt at lower temperatures than mafic Molten magma rises because it is less dense Mineralology: felsic (feldspar – silica) intermediate (andesite) mafic (magnesium – ferric) ultramafic (peridotites) – least amount of silica Largest crystals in the center of the flow Magmatic differentiation – different minerals crystalize at different temperatures Fractional crystallization – last to melt – first to crystalize Discordant intrusions: batholiths (plumes) veins stocks dikes Concordant intrusions: sill laccolith pluton Magmatic geosystems island arc plate subduction
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