Earth Science (Geology) Reviewer PDF

Earth Sci (Geology) The Planet Earth -​ Heated up by several processes Geology -​ Products of the impact of colliding dust -​ Systematic study of pres...

Earth Sci (Geology) The Planet Earth -​ Heated up by several processes Geology -​ Products of the impact of colliding dust -​ Systematic study of preserved records particles caused by natural processes -​ Compression of the interior of the earth developed by gravity triggered nuclear Chapter 1(me) reactions -​ Intense heat fed to the melting of various The Solar System materials and minerals that compose the earth Big Bang Theory - enormous quantities of matter formed and flung across space 3 Zones (compositional) -​ Core - center (heavier high density) Stars, local concentrations of mass that were -​ Iron, Ni, and some few minor collected by gravity, similar to these dust clouds elements formed protoplanets. -​ Liquid outer; solid inner -​ Mantle - lighter (low-density; float) Properties of planets -​ Iron magnesium, si, O2 -​ Orbits the sun -​ Peridotite -​ Enough mass to have a gravitational to -​ Olivine form a sphere -​ Unstable at -​ Dominant gravitational influence 400 km responsible for the absence of smaller -​ Pyroxene - 700 km objects along its orbit -​ Crust terrestrial planets -​ More chemically diverse -​ Mercury, venus, earth, mars -​ Planets nearest to the sun composed of Heating and subsequent differentiation led to the high temperature materials (e.g. iron, formation of 3 of the 4 subsystems nickel) Lithosphere, hydrosphere, atmosphere Jovian planets -​ Jupiter, Saturn, Uranus, Neptune (all Origin of Oceans elements are in the original condensed -​ From H2O found from water or gas in gas their crystal structures -​ Water minerals, interlocked in their -​ Minerals contain water or gas in crystalline structures structures water is released, then condensed to form oceans Prehistoric atmosphere -​ N2, CO2, NH4, S -​ No O2 Atmosphere -​ Diff densities. Same weight, -​ Connected to the formation of O2 identical cross-section -​ Started with cyanobacteria -​ Airy’s Hypothesis Vital statistics -​ Root of mountains -​ 150 million km away from the sun -​ Rocks have the same density but -​ Oblate spheroid unequal thickness float on a -​ Attributed to rotation of earth denser substratum stand at along its axis unequal heights compensated -​ Flattened poles by a root of its own material -​ Distance of the poles to the core that projects downward into the is high density “fluid layer” and displaces it -​ Bulging equator -​ Highly dense core, gravity pull is In ocean basins terrain is not all flat they have influenced by density seen using mountain ranges which is the oceanic ridge a surveying instrument aided by system (mid-atlantic ridge) a plumb bob P and S waves Eratosthenes (3rd Century) -​ P-waves have a hard time passing -​ Approximated the circumference of the through liquid or hot material earth -​ S-waves - cannot pass through liquids -​ Equatorial circumference is about 400k km So when a wave arrives late it says that there may be a liquid, or hot layer beneath Your weight in fort knox is heavier than being in a cave because of the density given that fort knox is Crust: 5-40 km thick full of gold Granitic - 35-40 km Basaltic 5 km Continental rocks (3.8 Bya) -​ Less dense Mantle- thickest layer, 80% of earth’s volume -​ Composed of Si, P, Na Mohorovicic (Moho) Discontinuity - division Oceanic rock (150 Mya) (basalt: Si, Fe, Mg) between crust and mantle Upper mantle - 400 km peridotite rock (Fe-Mg Isostasy (“equal standing”) rich) -​ Pratt hypothesis Lower mantle: 700-2,885 km -​ Mountains and plains (blocks – MgO, SiO2 FeO “floating” on an underlying Silicates unstable at 700 km layer of denser material at which their densities stand, inversely Lithosphere: related to the densities of the -​ Crust and upper mantle - solid two blocks Asthenosphere -​ Both mountains -​ Anything below  -​ Weak rocks or hot rocks Paleomagnetism -​ Rock’s contain magnetic record of Low velocity zone earth’s magnetic field direction at the -​ Seismic waves slow down when they time and place the rock’s were formed travel through this region -​ E.g. basaltic rocks (magnetite grains found) Gutenberg-Weichert Discontinuity - boundary -​ Change in magnetic polarity between mantle and core would change the direction -​ Differences in orientation PLATE TECTONICS would cause the stripe-like -​ Unifying theory of geology features which are found in the -​ Incorporates continental drift and ocean floor seafloor spreading Convection currents -​ Mechanism for seafloor spreading Alfred Lothar Wegener -​ Characterized by the high heat flows and Continental drift apparent volcanism along mid-oceanic -​ Pangaea ridges -​ Gondwana -​ Production of large convection cells in -​ Laurasia the in the mantle is brought about by the -​ Evidence differences in temperatures within the -​ Fossils of flora and fauna found in mantle different continents -​ The underlying event related to the -​ Rock formations and Geologic structure movement of plates towards each other is -​ Patterns of ancient climates brought about by descending convection currents - occurs in subduction zones Seafloor Spreading -​ Driving force behind the movement of -​ Harry H. Hess plates -​ Drifters vs Fixers -​ Found in the asthenosphere -​ Fixers -​ Land bridges -​ Evidence: -​ Ocean floor young in age (150 Mya) -​ Continents are older (3.8 Bya) -​ Suggesting that the ocean floor is more recently formed than continents -​ Where the old crust being destroyed: dense crust carried down to ocean trenches -​ Exemplified by rift valleys continents moved away from each other (e.g. Red sea)  THE GEOLOGIC ROCK CYCLE -​ Transformation of rocks and minerals indigo different forms due to different geologic processes 2 different approaches -​ Rock Cycle -​ Geologic history that conforms to the theory of uniformitarianism Movement of plates defines the existence of plate The formation of different rock types are boundaries products of different geological processes (magmatism, volcanism, sedimentation, Plate Boundaries: metamorphism) Divergent - spreading Convergent - important feature: ophiolitic complexes -​ Ophiolites: pieces of oceanic plates and the underlying upper mantle that have been uplifted onto the edge of continental plates Rock -​ Aggregate of one or more minerals -​ Composed of one or more minerals Classification of rocks (based on origin) From base to top the ophiolites is made of -​ Igneous peridotite, gabbro and volcanic rocks -​ Sedimentary The one that goes down is denser ​ -​ Metamorphic ​ - continent to continent -​ No subduction James Hutton - Ocean to ocean -​ Cyclic nature of geologic events - Ocean to continent (most likely to -​ Observations in Siccar point England happen; oceanic more dense) Principle of Uniformitarianism Transform - sliding -​ “The present is the key to the past”  -​ Laws of nature that now prevail have -​ Step 2: Deformation always prevailed -​ Step 3: Erosion - Unconformity -​ Rocks are formed by similar processes in -​ Step 4: Sediments on top of erosional the past surface -​ Step 5: Uplifting Steno’s Laws of Deposition -​ Nicholas Steno -​ Stratification or bedding Law of Superposition -​ Rocks are disposed in horizontal layers the oldest at the bottom the youngest at the top Law of Original Horizontality -​ Sediments deposited in water would GEOLOGIC HISTORY normally form horizontal layers -​ Pre-Cambrian -​ Cambrian Law of Lateral Continuity -​ Ordovician Silurian -​ When sediments are deposited in water -​ Devonian they spread laterally in all directions -​ Carboniferous -​ Permian Faunal Succession -​ Triassic -​ Fossils of organisms follow a vertical -​ Jurassic succession -​ Cretaceous -​ Tertiary Faunal Assemblage -​ Quaternary -​ Each strata or layer has its own assemblage of fossils Catastrophism vs uniformitarianism -​ Catastrophism Relative Dating Methods -​ Baron George Cuvier -​ Chronological arrangement of geologic -​ Caused by catastrophic events events comparing the physical -​ Earth 6k years old relationship of rocks and the fossils they -​ Uniformitarianism contain -​ Geological process are slow and gradual Law of Inclusion -​ A rock that is included into another is Siccar Point observations older than the one that encloses it (e.g. -​ Step 1: Sediments were deposited xenoliths) Usually found in igneous horizontally Law of Cross-cutting relationships ​ When Radioactive isotopes decay -​ Rock or structure that cuts another is produce another element which is called daughter younger than the one it cuts element -​ Faults, folds and dikes Unconformities Completely different from its parent element -​ Major interruptions in the geologic record Half-life - time it takes for half of the amount of the parent element to decay to its daughter Types: element Angular Unconformity Example: -​ Strata below the unconformity K-40 to Ar-50 distributed by folding and are titled with respect to the strata above Carbon-14 - absorbed by plants for photosynthesis NonConformity -​ Identified with layers of sedimentary Non-radiometric dating methods rocks or any layered rock above eroded Fission-track dating igneous or metamorphic -​ Determined b y counting the number of tracks that splitting U-238 Disconformity -​ Natural fission cracks are formed -​ Older beds below are parallel to the Paleontology younger beds -​ Studies of ancient life which may be used to determine the age of the fossil and consequently the rock GEOLOGIC LANDFORMS Geomorphology Absolute Dating -​ Study of landforms particularly their Radiometric description and interpretation as well as -​ Radioactivity is the spontaneous decay their evolution of elements by emitting particles and releasing energy Landform -​ Normally happens when an element -​ Individual topographic features (e.g. becomes unstable cliff) -​ 2 kinds of released particles -​ Alpha Topography -​ Beta -​ Surface condition of the earth -​ Radioactive isotopes are produced -​ Electron lost Relief -​ Electron captured -​ Manifests differences in elevation  -​ Non-metallic - vitreous or glassy, shine Structure (e.g. diamond) -​ Nature, arrangement and orientation of materials Hardness Processes -​ Resistance to scratching by another -​ Various actions that have combined to substance produce landorm -​ Controlled by atomic structure Slope -​ The stronger the bonding the harder the -​ Fundamental aspect of the shape of the mineral would be landform -​ (e,.g. Graphite and diamond) Drainage -​ Movement of water over the surface down into the soil and bedrock which influences the landform Different landforms are influenced by various internal and external geomorphic processes These processes consider the topography of the earth to be a surface of infinite variety Shells - carbonate MINERALS Definition of a Mineral -​ Naturally occurring, inorganically formed, homogeneous solid, with an ordered internal structure that is composed of atoms and ions, definite chemical composition and physical properties within a certain range Mohs Hardness scale -​ Can be expressed in a chemical formula -​ Friedrich Mohs (e.g. quartz) Color Physical and Chemical properties of minerals -​ Result of the spectrum of light with the spectrum the eyes can identify Luster -​ Don’t change color -​ Appearance of a mineral in reflected light -​ Magnetite, galena, azurite, malachite, -​ Metallic - Opaque, exhibits shine like a sulfur polished metal -​ Changes color  -​ Chalcopyrite Fracture -​ Variety of colors due to chemical -​ Separation in minerals other than the impurities (quartz) cleavage directions -​ Broken surfaces that are irregular and Streak nonplanar -​ Color of the powdered form of the (e.g. Quartz and volcanic glass) mineral -​ Color of mineral is different from streak Parting is the separation among planes of -​ E.g. pyrite: color: gold, streak black structural weakness which are the results of crystal twinning or pressure Mineral structure and crystal form -​ Crystalline structure -​ Regular arrangement of atoms Specific gravity -​ E.g. Graphite and Diamond -​ Ratio between the volume of the (Both made of carbon but substance and the weight of the same different structure) volume of water -​ Crystal Habit -​ Numerically equal to density -​ Internal arrangement of the atoms and molecules Chemical composition -​ 7 crystallographic systems -​ Few minerals that are composed of a -​ Cubic, hexagonal, trigonal, tetragonal, single element orthorhombic, monoclinic, triclinic -​ Diamond (C), copper (Cu), Gold (Au), Sulfur (S) Identification Luster → Hardness→ Color → Streak → Crystal form/habit → Cleavage → Specific gravity Classification of Minerals Oxides: Magnetite Sulfides: pyrite Sulfates: gypsum Cleavage Carbonates: Calcite, dolomite -​ Natural tendency of the mineral to split Phosphates: Apatite into different planes Halides: chlorine -​ Lines of weakness Silicates: feldspar -​ Parallel to the atomic planes -​ Calcite, 120 and 60 degree angles 8 elements that make up 98% of earth’s crust -​ Oxygen, Silicon, Aluminum, Iron, Calcium, Sodium, Potassium, and Magnesium Compositional variation -​ Minerals that cannot be expressed in simple formulas -​ Brought about by ionic substitutions that make solid solutions -​ Ionic substitution -​ One element can substitute another without changing the crystal lattice Stability of Minerals Field of stability -​ Natural state within certain, temperature, pressure and chemical environment Presented in phase diagrams or phase equilibria Graphical representations of the phase rule -​ Which shows stability of phases in a system under various conditions