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Geology 102 Marli Miller - Midterm

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by: Chloe Nightingale

Geology 102 Marli Miller - Midterm 102

Marketplace > University of Oregon > Geology > 102 > Geology 102 Marli Miller Midterm
Chloe Nightingale
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A detailed study guide for the first Midterm in Marli Miller's 102 Geology class
Marli Miller
Study Guide
Geology, Marli Miller, GEOL102, Geology Midterm, midterm
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"Great notes!!! Thanks so much for doing this..."
Everette Rosenbaum

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This 8 page Study Guide was uploaded by Chloe Nightingale on Monday February 1, 2016. The Study Guide belongs to 102 at University of Oregon taught by Marli Miller in Winter 2016. Since its upload, it has received 45 views. For similar materials see in Geology at University of Oregon.


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Date Created: 02/01/16
Geology Midterm Definitions Rock: A coherent, naturally occurring solid, consisting of an aggregate of minerals, or,  less commonly, of glass.  Cement: What bonds rocks, mineral material that precipitates from water and fills the  space between grains.  Clastic: Rocks that are held together by cement Crystalline: Rocks whose crystals interlock with one another, rocks that originate as a  continuous mass.  Bedrock: Rock that is still attached to the earth’s crust Outcrop: An exposure of bedrock Igneous rocks: Rocks that form by the freezing of molten rock. They cool and crystalize  to form a liquid state. Lava= extrusive and magma=intrusive. Extrusives are finely  grained and intrusives are not. Examples: Intrusive=granite and extrusive= basalt.  Sedimentary rocks: Rocks that form by either the cementing together of fragments  broken off pre­existing rocks or by the precipitation of mineral crystals out of water  solutions at or near the Earth’s surface. Bedded. Can be clastic (broken particles),  biogenic (precipitated from biological activity), or chemical (precipitated through  chemical processes). Examples: Sandstone, limestone, or rock salt.  Metamorphic rocks: Form when preexisting rocks change character in response to a  change in pressure and temperature conditions. Foliated (layers). Does not involve  melting. Usually crystalline and found at mountain belts and subversion zones.  Equant: Same dimensions in all directions Inequant: Dimensions are not the same in all directions Bedding: The layering of sedimentary rocks Foliation: The layering of metamorphic rocks Hand specimen: A fist­size piece of rock  Lithosphere: Consists of the crust plus the top (cooler) part of the upper mantle, behaves rigidly, floats on the asthenosphere.  Asthenosphere: Relatively soft layer composed of warmer mantle that can flow slowly  when acted on by a force, convects like water in a pot on the stove. The continental lithosphere is much thicker than the oceanic lithosphere. The  continental lithosphere floats at a higher level because it is composed of lower density  felsic and intermediate rock.  Lithosphere plates: Plates that exist because the lithospheric shell contains a number of  major breaks. There are 12 major plates and also microplates.  Plate boundaries: Breaks between plates Earthquakes: Vibrations caused by shock waves that are generated where rock breaks  and suddenly slips along a fault, occur in narrow and distinct belts.  Active margins: Plate boundaries Passive margins: Not plate boundaries, continental crust is thinner here and sediment  covers it up.  Continental shelf: The surface of the sediment covering passive margins, broad and  shallow. Fish hang out here.  Divergent boundary: Plates move apart from each other Transform boundary: Plates slide sideways past each other Convergent boundary: Plates plates move toward each other and one sinks beneath the  other Relative age: The age of the rock in respect to another Numerical age: Age of a rock in years Principle of uniformitarianism: Physical processes that operate in the modern world  also operated in the past at roughly the same rates. Responsible for forming geologic  features preserved in outcrops.  Principle of original horizontality: Layers of sediment, when first deposited, are fairly  horizontal because sediments accumulate on surfaces of low relief in a gravitational field. Principle of superposition: In sedimentary rock layer, each layer must be younger than  the one below.  Principle of lateral continuity: Sediments generally accumulate in continuous sheets  within a given region.  Principle of cross cutting relations: If one geologic feature cuts across another, the  feature that has been cut is older.  Principle of baked contacts: An igneous intrusion “bakes” surrounding rocks, so the  rock that has been baked must be older than the intrusion.  Principle of inclusions: A rock containing an inclusion (fragment from another rock)  must be younger than the inclusion.  Geologic history: The succession of events in order of relative age that have produced  the rock, structure, and landscape of a region.  Fossil assemblage: The group of fossil species The principle of fossil succession: Extinction is forever. Once a fossil disappears at a  horizon in a sequence of strata, it never appears higher in the sequence.  Index fossils: Fossil species that are widespread, but survived only for a relatively short  interval of geologic time. Angular unconformity: Rocks below an angular unconformity were tilted or folded  before the unconformity developed.  Nonconformity: Sedimentary rocks overlie generally much older intrusive igneous rocks and/or metamorphic rocks. The igneous or metamorphic rocks underwent cooling, uplift,  and erosion prior to becoming the substrate on which new sediments accumulated.  Disconformity: The boundary between a new sequence of sediment and the old sediment below it Isotopic dating: Using measurements of radioactive elements to calculate the numerical  ages of rocks.  Geochronology: The study of numerical ages Radioactive decay: The process isotopes undergo when they’re unstable, converting  them to another element.  Parent isotope: The isotope that undergoes decay Daughter isotope: The element that emerges after decay Half­life: How long it takes for half a group of parent isotopes to decay.  Isotopic dating techniques: Find unweathered rocks, separate the minerals by crushing,  extract parent and daughter isotopes by dissolving the minerals in acid, analyze the  parent­daughter ratio with a mass spectrometer. Closure temperature: The temperature below which isotopes are no longer free to  move.  Radiometric dating: Dating geologic events in years by measuring the ratio of parent  isotopes to daughter product atoms.  Relative age: The age of a geologic feature in relation to another.  Main Points ­How to distinguish rocks:  Grain size: Dimensions of the grains in a rock, measured in mm or cm  Composition: Proportions of the different chemicals making up the rock  Texture: Arrangements of the grain in the rock  Layering: Defined by bands or grains that trend parallel to each other ­Names of rocks usually come from the dominant component making up the rock, the  region where the rock was first discovered or is abundant, the root word of Latin origin,  or the traditional name used by the people in an area where it is found.  ­Steps in studying a rock: Identify a rock Develop a hypothesis for how it formed Make a very thin slice (thickness of human hair) Observe under a petrographic microscope  (illuminates a thin section) Identify the grain and its orientation Make a record of the image using a camera through  the microscope (the picture is called a photomicrograph) ­The rock cycle  Material can enter when magma rises from the mantle  Refer to diagram in notes!!  The material that makes up any type of rock can turn into any other type of rock  given the right combination of processes.  These processes are:  o Weathering erosion o Lithification: Transformation of loose sediment into solid rock  o Burial o High temperature and pressure o Melting o Cooling o Crystalizing o Uplift and erosion o Metamorphism: Changing of a rocks, chemical composition by reactions  with hydrothermal fluids o Volcanism ­Geologic time scale!!! Diagram in notes.   Precambrian   Paleozoic (Phanerozoic)  Mesozoic (Phanerozoic)  Cenozoic (Phanerozoic) ­Weathering and erosion  Weathering: The breakdown of material at the Earth’s surface  The surface has less pressure, lower temp, oxygen­rich atmosphere, and acidity in waters    Mechanical weathering o Reduces the size of rocks and depends on properties o Frost wedging: Water seeps into frozen rock and ice makes it expand o Crystal growth: Rock absorbs water, water evaporates, crystals grow and  crack rock o Thermal expansion: Enlargement of crystals due to heat. Chemical bonds  are weakened.  o Mechanical exfoliation: Overlying rocks apply pressure, expand upon  erosion. o Biological disturbance: Tree root growth, animals burrowing o Abrasion: Scraping and sculpting by loose particles such as glaciers,  rivers, and wind    Chemical weathering o Alters the composition of the rock, typically occurs through the flow of  water. Natural rainwater is slightly acidic.  o Dissolution: Water removes mass in solution, uses carbonic acid and acid  rain to dissolve the rock.  o Hydrolysis: Granite materials are altered to clay minerals by H+ and OH­ o Oxidation: Elements lose electrons when combined with oxygen. Iron  oxides are formed.  o Factors that affect chemical weathering: Surface area of minerals, contact  time with water, strength of chemical bonds, biological influence, and  climate moisture and temperature.  ­Mass wasting types  Mass wastings are natural hazards, move along the rock cycle, control the height  of mountains, have socioeconomic impacts, and have biological functions.   Types of mass wasting types are determined by the types of material, velocity,  and environment or setting.   Caused by convergent margins, collisional orogeny, rifts, volcanoes, human  deposition, sea level drop, and displacement.   Triggered by rainfall/snowmelt, shocks/earthquakes, undercutting, and strength  loss due to weathering or vegetation change.   Intact rock is very strong; fractures decrease strength.   Gravitational forces vs. frictional forces. Frictional forces provide stability.   Creep: Slow, continuous process that occurs on soil­mantled slopes. Driven by  freeze­thaw cycles and biological disturbances.  Slumping: Headscarp that fractures at the top and folds at the toe with a bench­ like deposit. Hummocking terrain like a golf course with a discrete failure surface.  Flows: Mixture of rock, soil, and water. Velocity varies with steepness, speed,  and material.  o Earthflows: Highly vicious and slow moving deeply weathered soil and  rock. Deposits on moderate slopes.  o Debris flows: Course grained materials with a low viscosity (more water).  Deposits on gentle slopes.  o Mudflows: Fine­grained material with a very low viscosity. Deposits on  gentler slopes.  o Lahars: Volcanic ash and water that’s eruption or rain related with  scalding lobes.   Rockslides: Travel as coherent mass initiate along a plane of weakness  Rockfalls: Loose rock on steep cliffs with a very high viscosity (160mph) ­Water properties  Two hydrogen atoms bound to an oxygen, with a bond angle of ~106° –creates a  polar molecule.  Bonds to other water molecules via hydrogen bonds.  Water has these special properties: Capillary action, High surface tension, remains liquid over a wide range of temperatures, Is a powerful solvent, has a high heat  capacity, has latent heat of vaporization, is denser than ice. ­Plate tectonics  The lithosphere is broken up into plates that move over the asthenosphere  Convergent margins: Subduction zones; one plate is more dense than the other  and slides under.   Divergent margins: Formed at mid­ocean ridges. Ocean floor spreads apart and  forms a ridge. New basalt erupts at the divergent margin and fills the gap, making  new ocean floor.   Transform faults: Link other plate boundaries and connect and support  unconnected ridges.   The PNW subduction zone, divergent margin, and transform fault:   Hypothesis:  Scientific theory:


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