Geology-110 Midterm GEOL 101 001
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GEOL 101 001
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GEOL 101 001
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This 14 page Study Guide was uploaded by Ashley Burgiss on Saturday September 24, 2016. The Study Guide belongs to GEOL 101 001 at University of South Carolina taught by Dr. Scott M. White in Fall 2015. Since its upload, it has received 9 views. For similar materials see Introduction to the Earth in Geology at University of South Carolina.
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Date Created: 09/24/16
Midterm Review Structure of the Universe and Earth’s Systems 1. Ancient people believed the Universe was geocentric a. Earth sat at the center of the Universe b. Moon, planets, and stars circled around the motionless Earth c. Ptolemy (100170 C.E.) proposed equations to predict the movement of the planets th d. Heliocentric model came to in the 15 century with the Renaissance 2. Modern Era: Universe is made up of matter and energy a. Matter (mass, density, weight): subjects that take up space (stuff) b. Energy (heat, light, pull of gravity): the ability to do work 2 c. E=mc d. Big Bang occurred 13.7 billion years ago i. Converted pure energy into matter (the first matter of the universe) ii. Our solar system has only been around for 5.4 billion years, and it did not form during the Big Bang iii. The third protoplanet from the Sun became Earth. Temperatures rose in the center of the Earth, evening out the surface due to the softness of the Earth and the pull of gravity on it. The Earth cooled, its crust became solid, and meteorites kept hitting the planet which caused Earth to melt and cool over and over again. One meteorite was large enough that, when it collided with the Earth, it vaporized most of both bodies. The debris from this impact was sucked in the Earth’s pull of gravity, coming together and creating the moon. Therefore, the oldest Earth and the oldest moon rocks are the same age. iv. Earth used to be much bigger before the Big Bang v. Material that formed the solar system was created by the supernova phenomenon 3. Earth system a. Atmosphere: gaseous envelope i. Powered by sunlight ii. Primarily Nitrogen (78%) and Oxygen (21%) b. Hydrosphere: blue, liquid water i. Powered by sunlight ii. Earth is 30% land, 70% water c. Biosphere: wealth of life i. Powered by sunlight d. Lithosphere: solid Earth i. 32% Iron, 30% Oxygen, 15% Silicon, 14% Magnesium, 8.8% 88 other elements ii. Oxygen and Silicon are main components of the rocks around us e. The Earth’s layers i. Lithosphere (crust) ii. Asthenosphere iii. Mesosphere iv. Inner and outer core Vocabulary Closed system: operates within itself (Earth is a closed system) Open system: pulls in resources from somewhere else to operate Nebula system: formation of the solar system Doppler Effect 1. Sound waves compress or relax with relative motion a. Compressed: shorter wavelengths, higher frequency b. Relaxed: longer wavelength, lower frequency 2. Influences light a. Visible light = electromagnetic radiation b. Red light: Longer wavelength, shorter frequency i. Light moving away from an observer expands ii. Light from galaxies observed described as “redshifted” iii. Edwin Hubble deduced that the Universe must be expanding (raisin bread dough model) c. Purple: shorter wavelength, longer frequency i. Light moving towards a subject compresses Vocabulary None Plate Boundaries 1. Divergent Plate Boundaries a. Seafloor Spreading Ridge (seafloor spreading proposed by Henry Hess in 1960s) i. When two plates each carrying oceanic crust move apart ii. Asthenosphere beneath rises and melts, producing a magma chamber, either filling vertical cracks to the surface or creating submarine volcanoes b. Continental Rift i. Plate carrying continental crust moves apart ii. Volcanic bulge created because of thinning lithosphere and the asthenosphere pushing up and through (as lithosphere mantle stretches, the cool and brittle crust above fractures and faults develop, creating large fault blocks of crust that slide down into the widening rift) 2. Convergent Plate Boundaries a. Volcanic Island Arc i. Convergence of two plates carrying oceanic crust (subduction of one plate under another) ii. “Subduction trench” forms where subducting plate bends downward into the mantle iii. Sediment on the crust of subd. plate is scraped to the edge pf the overriding plate, creating a wedgeshaped feature (accretionary prism) and magma (created by flux melting of mantle above surface of subd. slab) rise through overriding plate iv. Builds underwater volcanoes and volcanic islands, resulting in a chain of underwater volcanoes parallel to the subd. zone b. Continental Volcanic Arc i. Convergence of two plates (one oceanic, one continental) results in subd. of oceanic under continental (all subducting plates are oceanic because continental crust isn’t dense enough to sink) ii. Sediment accumulated on crust of subd. plate scrapes onto the edge of the overriding plate, forming an accretionary prism (terrestrial sediment from continent accumulates in the fore arc basin between the coastline and prism) iii. Magma erupts and forms volcanos and forms a chain along the margin of the continent c. Continental Collision i. Because continental crust cannot subduct, the two continental plates “smush” together ii. Crusts fold, fault, and plastically flow, resulting in significant thickening of crust in collision zone, resulting in a tall mountain range above and a deep crustal root below iii. “fold and thrust belt” formed when crust along the edge of mtns are faulted and folded 3. Transform Plate Boundaries a. Fracture Zone i. Midoceanic ridges are not continuous, but consist of short ridge segments. Individual segments are laterally offset from one another at right angles by fracture zones. ii. As new crust is formed at the seafloorspreading ridge, and older crust continuously moves away from the ridge axis, part of the fracture zone will be located between adjacent seafloor crust moving in the same direction. iii. Littletono relative motion occurs on these lengths of the fracture zone, however, where seafloor is moving away from offset ridge axes in opposite directions, the fracture zone acts as a transform boundary iv. Additional source of earthquakes along the midoceanic ridge b. Plate Margins i. When two plates slide past each other ii. Results in a great amount of earthquake activity Vocabulary Suture: boundary between onceseparate plates Subduction: when one plate goes beneath another Fault: crack in the Earth’s crust Continental Drift and Paleomagnetism 1. Alfred Wegener (glaciologist) proposed the theory of continental drift in 1915 after finding evidence a. The continents fit together like a puzzle (Africa and North and South America: Niger delta overlap) b. Fossil evidence of freshwater dinosaurs found in South America and Africa (freshwater dinosaurs would have had to cross a saltwater space) c. Rock type and structural similarities i. Matching mountain ranges (Appalachian, British Isles, Western Africa, and Caledonian) d. Paleoglacial evidence i. Southern tips of South America, Africa, India, and Australia ii. Glaciers from Antarctica run over rocks iii. Yosemite, Half Dome e. Issues i. Wegener could not explain what happens to the seafloor as it moves ii. Believed continental drift to occur quickly 2. Paleomagnetism a. Magnetized mineral in rocks i. Show distance to Earth’s magnetic poles when that rock was formed ii. Provide the latitude at formation iii. More inclination equals higher latitude b. Geomagnetic inclinations c. Apparent polar wander i. Rocks in Europe and North America point to different North Poles ii. Poles get farther apart when further back in the past iii. Apparent polar wander shows us how far away the north magnetic pole was in terms of latitude d. Polar wandering i. Poles match if continents are placed next to each other ii. Pole indicates North America and Europe were near the equator when coal deposits were forming iii. Reconciled by continental drift e. Geomagnetic reversals i. Earth’s magnetic field periodically reverses polarity ii. Dates when the polarity changes were determined from lava flows recorded in ocean crust Vocabulary Inclination: how inclined the needle gets the farther away from the equator one gets Pangaea 3. One of several supercontinents in the past few billion years a. Subcontinents form when subduction consumes ocean basins and continents on either side of the ocean collide b. Breakup occurs through continental rifts 4. Pangaea came into existence at the end of the Paleozoic when Laurentia (a land mass composed of North America and Greenland) collided with Gondwana (land mass containing Africa and South America) a. Appalachian Mountains are leftovers of this collision (a dinosaur living in early Mesozoic could have walked from Canada to South Africa) 5. Triassic continental rift basins developed as supercontinent drifted apart 6. Jurassic (2 mil years ago) Pangaea broke apart a. Rifts formed along the east coast of North America and rifting succeeded, establishing midAtlantic ridge and North America started to grow b. S. America split from Africa and South Atlantic started to grow c. Complex plate boundaries developed in region between North & South America (Caribbean Sea) 7. Seafloor spreading in central North Atlantic happens at 3 cm/year aka the ocean basin is getting wider 3 km/mil. years or 300,000 km/100 million years 8. Hot Spots (ex: Hawaiian Islands) a. Hot spots volcanoes are probably a consequence of mantle plumes b. As plate drifts over hot spot, a chain of volcanoes forms c. Over time, a hot spot volcano island erodes and subsides, eventually sinking below sea level to form a seamount d. Ridge push developed by the gravitational energy associated with the topographic elevation of the midocean ridge 9. Slab pull: what drives the movement of the ocean’s lithosphere Vocabulary None Minerals 1. The nature of chemical bonding governs mineral properties a. Rarity b. Beauty c. Value d. Color e. Mystique 2. Physical properties a. Color b. Luster c. Streak d. Hardness e. Specific gravity f. Crystal habit g. Cleavage 3. Mineral Families a. Silicates: most important and most abundant because they are made of silicon and oxygen (most of the Earth’s crust) i. Fundamental building block of silicate minerals is siliconoxygen tetrahedron b. Oxides: oxygen bonds with metallic cations to form important ore mineral oxides c. Sulfides: combines with metallic cations to form many of our important metal ore minerals 2 d. Sulfates: contain the SO 4 many made from the evaporation of seawater e. Halides: minerals that have halogens as their dominant anion (ex: salt) f. Carbonates: contain the carbon anion i. Soft minerals that fizz in dilute hydrochloric acid g. Native elements: minerals that occur as a single element 4. Minerals in the Earth’s Crust a. Oxygen, Silicon, Aluminum, Iron, Calcium, Sodium, Potassium, Magnesium 5. Crystals a. Single, inorganic, continuous piece of crystalline solid, typically bounded by flat crystal faces b. Faces grow naturally as the mineral forms and reflect atomic structure c. Atoms are arranged in a specific geometric pattern d. Mineral are the building blocks of rocks e. Law of Constancy and Interfacial Angles i. Equivalent faces found on two samples of the same mineral always bear the same angular relationship f. Gemstones i. Singlecrystal minerals that are durable, rare, and beautiful (as described by the five c’s: clarity, color, cut, carat, certification) Vocabulary Cleavage: the tendency of a mineral to break along flat planar surfaces as determined by the structure of its crystal lattice Metallic: of or relating to metal Types of Rocks 1. Igneous rocks a. Come from molten earth (magma) b. “Lava” if magma reaches the surface, “pluton” if magma is stuck at depth c. Controlling factors i. Temperature, pressure, mixing or assimilation of host rocks d. Have holes 2. Metamorphic rocks a. Core of mountains b. Changes to original rock texture or mineral assemblage by temperature or pressure c. Controlling factors i. Compositions of parent rock, temperature, pressure d. Increasingly coarse “foliated rocks” i. Shale slate phyllite schist gneiss migmatite 3. Sedimentary rocks a. There are two types of sedimentary rocks, based on the source of the material: detrital rocks, which are transported sediment as solid particles (clastic); and chemical rocks, which are dissolved rock (like salt left over from evaporated water) and transported as liquid. b. Types of sedimentary rocks are determined by two major textures: clastic and nonclastic. Clastic rocks are discreet fragments and particles and they have a clastic texture. Nonclastic rocks have a pattern on interlocking crystals and may resemble an igneous rock. c. Shale is a type of detrital rock. It has mudsized particles in thin layers that are commonly referred to as laminea. It is the most common sedimentary rock. d. Sedimentary Structures i. Provide information useful to the interpretation of Earth history ii. Types of sedimentary structures 1. Strata, or beds (most characteristic of sedimentary rocks) 2. Bedding planes that separate strata iii. Sedimentary Bedding 1. Layers of rock deposited over time 2. Tells us what the environment was like at the time 3. Example: Grand Canyon 4. The surface between two units of sediment is called a contact 5. Angular beds? Result of crossbedding a. Orientation indicates wind direction at the time of deposition e. Clastic: pieces of other rocks (ex: sandstone) f. Chemical: precipitated from dissolved solution (ex: salt) g. Organic: remains of organisms (e: coal or fossils) h. Products of mechanical and chemical weathering i. Account for about 5% (by volume) of earth’s outer 10 miles j. Contain evidence of past environments k. Provide info about sediment transport l. Often contain fossils Chemical Sedimentary Rocks 1. Consist of precipitated material that was once in aqueous solution (ex: coal) 2. Precipitation of material occurs by a. Inorganic processes b. Organic processes (biochemical origin) 3. Limestone a. Most abundant chemical rock b. Composed chiefly of the mineral calcite c. Biochemical d. Form as coral reefs and chalk (microscopic organisms) i. “Carbonate platforms” 4. Evaporites a. Evaporation trigger deposition of chemical precipitates b. Examples: rock salt and rock gypsum (drywall) c. Salt is impermeable 5. Coal a. Different from other rocks because it is composed of organic material b. Stages in coal formation i. Plant material ii. Peat 1. Partiallyaltered plant material 2. Smoky when burned 3. Low energy iii. Lignite 1. Soft, brown coal 2. Moderate energy iv. Bituminous (the one Santa brings) 1. Soft, black coal 2. Major coal used in power generation and industry 3. High energy v. Anthracite (shinier than Bituminous; Santa might bring it if he’s feeling nice) 1. Hard, black coal 2. Used in industry 3. High energy Vocabulary None Rock Cycle 1. Steps a. Weathering b. Erosion c. Transportation d. Deposition (sedimentation) e. Lithification (burial and diagenesis) 1. Weathering a. Physical breakdown (disintegration) and chemical alteration (decomposition aka dissolving) of rock at Earth’s surface b. Main source of sediment c. In contrast to i. Mass wasting – transfer of rock and soil downslope under the influence of gravity ii. Erosion – physical removal of material by mobile agents such as water, wind, ice, or gravity d. Mechanical Weathering i. Breaking of rocks into smaller pieces ii. Types 1. Frost a. Ice trickles down into rock, freezes and expands, cracks rock 2. Unloading aka Exfoliation a. Land on top of deep pluton (igneous rock) erodes, releases pressure, expands, sheets parallel to the surface of the earth appear, sheets break off 3. Thermal expansion a. Rock expands, out layers crack and break off (might happen in a wildfire) 4. Biological activity (tree roots, etc.) a. Breaking of rock apart by prying into the middle by (ex: tree root) e. Chemical Weathering i. Dissolution 1. Aided by small amounts of acid in the water (ex: acid rain) ii. Oxidation 1. Any reaction when electrons are lost from one element (ex: rust) iii. Hydrolysis 1. Reaction of substance with water 2. Hydrogen ion attacks and replaces other ions 2. Transportation a. Transport agents i. Water (less effective than ice) aka rivers, ocean currents, tides ii. Wind iii. Ice iv. Ice (glaciers) v. Effects 1. Sorting 2. Rounding b. Turbulence i. Turbidity currents caused by underwater avalanches of sediment 1. Called turbite 2. How continental shelves are formed ii. Current slows and deposits sediment in a submarine fan iii. Water and sediment flow downslope iv. After current settles, the coarser grains are at the bottom and the finer grains are at the top Vocabulary None Mass Movement 1. Massmovement (aka masswasting aka erosion) a. Downslope motion of rock, regolith (soil, sediment, debris), snow, and ice b. Driven by gravity c. Component of rock cycle d. Ex: landslide 2. Classification a. Type of material (rock, regolith, snow, ice) i. Unconsolidated sediment (mud, earth, debris) ii. Rock b. Rate of movement (fast, intermediate, slow) i. Fall (freefalling pieces) ii. Slide (material moves as a single block) iii. Flow (material moves as a chaotic mixture) 1. Mudflows/debris flows/lahars are mass movements that have a greater water content (a lot of rain can trigger a flow) 2. Lahar is a special volcanic mud or debris flow (volcanic ash mixes with water from heavy rains or glacier melts) iv. Creep is the slow, downhill movement (slowest movement) @ 1km/hr 1. Creep is evident from tilting landscape features v. Solifluction is the slow, downhill movement of tundra (melted permafrost slowly flows over deeper, frozen soil) vi. Slumping is mass movement by sliding of regolith as coherent blocks (shows as spoonshaped “failure surface”) vii. Avalanche – debris and air (usually snow) and wet avalanches (slower) vs. dry avalanches (fast movement of cold, powdery snow) 3. Landslide Potential Mapping a. Scientists look at i. Slope steepness ii. Strength of substrate (loose or tightlypacked sediment) iii. Degree of water saturation iv. Orientation of planar features v. Beddings vi. Joints vii. Foliation viii. Vegetation cover ix. Heavy rain production x. Undercutting potential xi. Earthquake probability 4. Slope angle controlled by a. Particle size b. Shape c. Surface roughness 5. What trigger mass movement? a. Shocks, vibrations, and liquefaction b. Changes in slope loads, steepness, support c. Changes in slope strength 6. Preventing mass movements a. Identify potential failure planar and revegetate b. Regrading (steplike slopes) by terracing c. Dewatering (lowering water table) d. Reducing undercutting (riprap blocks) e. Retaining walls using gummite Vocabulary None
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