GEOL 1330 (Hauptvogel Spring 16) TEST 2 STUDY GUIDE
GEOL 1330 (Hauptvogel Spring 16) TEST 2 STUDY GUIDE GEOL 1330
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This 12 page Study Guide was uploaded by Julian Quesada on Monday March 7, 2016. The Study Guide belongs to GEOL 1330 at University of Houston taught by Dr. Daniel Hauptvogel in Spring 2016. Since its upload, it has received 153 views. For similar materials see Physical Geology in Geology at University of Houston.
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Date Created: 03/07/16
GEOL 1330 EXAM 2 STUDY GUIDE 30 questions, multiple choice, true/false -Volcanoes lecture Types of Lava -High Viscosity - magma doesn’t flow easily (flows slowly like syrup) -Higher silica content -More silica-oxygen tetrahedra sticking together -Traps gasses, allowing pressure to build up -Violent eruptions -Low Viscosity - magma flows easily (like water) -Lower silica content -Magmas allow gases to migrate up and escape -Passive eruptions -Felsic and Intermediate gives explosive eruptions -Mafic and Ultramafic are not explosive -Top Hat question -Which type of geologic setting are you most likely to find explosive volcanism -Answer: Subduction Zone -90% of all lava erupted is basaltic (mafic) in composition -Non-violent volcanism -4 types of lava flows -aa "ah-ah" -Pahoehoe "poh-hoy-hoy" -block -pillow -Aa: Flows have rough jagged blocks with sharp edges -mafic -Pahoehoe: flows have smooth surfaces, resembling twisted braids of ropes -Mafic -Pillow: lavas have stacked tube-like structures -Found at divergent boundaries -Mafic -Block: flows are short and thick, with massive curved/smooth blocks -Intermediate/felsic -Remember that magma/lava contains dissolved gasses -Released during eruptions -Gas content of basalt (Important - Quiz/test question) -70% - H2O -15% - CO2 -5% - N -5% - SO2 -Trace - Others: e.g. Cl, He, Ar, F -Pyroclastic Materials are pulverized rock and lava fragments from within the volcano Types of Volcanoes -Shield Volcano - Mainly basaltic lavas -Gentle slopes of 2 to 10 degrees -Up to 120km wide -Long-lived 10,000's yrs, non-violent eruptions -Basaltic (Low silica) Magma -Cinder Cone - Mainly basaltic pyroclastic material -Slopes of ~30 degrees -Only ~1km wide -Short lived, typically a single event -High Silica Magma -Composite Volcano - Alternating pyroclastic deposits and andesitic lava flows -Very steep slopes -~10-15km wide -Intermittent, highly explosive eruptions -Erupts and goes dormant until pressure builds up. Rinse and repeat -High Silica Magma -Sediments Physical Weathering -Weathering: The physical and chemical processes that breakdown rocks -Physical Weathering: processes that physically break apart a rock (river, avalanche, etc.) -Chemical weathering: chemical transformation of a rock into new compounds (rust, melting, etc.) -Physical (mechanical) weathering includes: -Frost wedging: Occurs when water freezes in the cracks of rocks -As water freezes it expands, and can cause the rocks to break -Sheeting/exfoliation: Occurs due to a decrease in pressure -Biological activity can wedge rocks apart as plant roots grow in cracks (root wedging) -Can also create acids to chemically weather rocks -Other physical weathering processes include: -Tectonic stresses -Thermal stresses -Freezing and thawing -Abrasion by wind/water -Powerful wave action at the shoreline -Salt crystallization in cracks -Expansion/contraction of wet/dry clay Chemical Weathering -Types of chemical weathering include -Dissolution: happens when a solid (rocks and minerals is dissolved into ions -Water is actually a great solvent -So is acid -Oxidation: occurs when an element loses electrons -e.g. rusting -Responsible for red coloring in many rocks -Hydrolysis: occurs when hydrogen ions replace other positive ions (cations) found in the crystal structure -The primary way silicate minerals decompose -Occurs in water or acidic conditions -This replacement creates new minerals -Water with a lot of dissolved ions is referred to as "hard" water -If you have hard water at home, the dissolved ions react with soap, making it seem like you can't get soap off Weathering Rates -The rate at which rocks and minerals weather is primarily controlled by -Top Hat Question -These gravestones were created around the same time, yet look different from one another. What is the best explanation? (The gravestone on the right has an eroded face, whereas the one on the left looks normal) -The rocks used for the gravestone on the left is more resistant to weathering -Rock on left is granite and rock on right is marble. Marble is calcite rich which is very susceptible to weathering -Differential weathering*** is when one material weathers easier and faster than another -Usually due to differences in mineral composition and atomic structure Soil Formation -Weathering is a key process in the formation of soil -Soil: combination of minerals, organic matter, air, and water -Soil formation is controlled by -Parent material: Affects the rate of weathering (and thus soil formation) and fertility -Time: The longer a soil has been forming, the thicker it becomes and the less it resembles the parent material -Climate: the most important factor in soil development -Temperature and precipitation -Hot and wet = heavy chemical weathering -Cold and dry = heavy physical weathering -Plants and Animals: Affect the physical and chemical properties -Mixing of the soil by borrowing organisms -Most organic matter comes from plants -Topography: Soils develop poorly on steep topography -Top Hat Question -Which do you think is the primary factor in soil -Climate -Precipitation and temp control break down of rocks and therefore, production of soil Transport and Deposition of Sediments -Sedimentary rocks cover 75% of the land area -Most of the ocean floor is covered by sediments -The igneous rocks are underneath the sediment -They contain evidence for past environments and are economically important -Coal -Petroleum and natural gas -Sources of iron, aluminum, and manganese -Most fossils are found in sedimentary rocks -Sediment is material derived from physical and chemical weathering of rocks which is deposited on the surface of the Earth -Erosion: The transport of sediment from its original site to a location where they accumulate -Wind - can move the sediment, typically the smallest particles with light wind and larger with stronger wind (arid regions) -Water - Rivers carry sediment to the ocean (Continents) -Ice - In the polar regions/mountains, ice is moving at a very slow rate (polar) -When the wind or water slows down, or if the ice melts, the solid sediments are deposited -Deposition of material dissolved in water occurs when there are chemical or temperature changes that allow this material to crystallize (precipitate) -As deposition continues, older sediments are continually buried beneath younger sediments -Sedimentary rocks are produced through lithification of these deposited sediments -Compaction and Cementation -Cementation: As water is squeezed out of the pore spaces by pressure, dissolved ions will precipitate and form the "cement" that holds a sedimentary rock together Detrital Sedimentary Rocks -Detrital (clastic) rocks are primarily composed of quartz and clay materials -Most other minerals weather into new substances (e.g. clay minerals) -If minerals like feldspars and micas are present, this indicates erosion and deposition occurred quickly -Rock name is determined by grain size -Grain Size: Size of sediments making up the rocks -Fine grained rocks will feel smooth to the touch -Shale: Brittle (breaks easy), and has thin layers -Mudstone/Siltstone: Blocky, deposited in Low energy environments -Lakes, Slow rivers, deep ocean -Sandstone: Medium to coarse grained, sand sized grains. Feels gritty like sandpaper. Deposited in higher energy environments -Shorelines, fast moving rivers -Sorting - grain size variability -Conglomerates and breccias have larger clasts in a finer grained matrix -Conglomerates - Have rounded clasts -Breccias - Have angular clasts Chemical Sedimentary Rocks -Precipitation of material occurs by -Inorganic processes -Water is super-saturated with an ion -Organic processes (biochemical) -Precipitation of ions that form shells for organisms -When they die, their shells accumulate on the ocean floor -Limestone: The most common chemical sedimentary rock -Composed chiefly of the mineral calcite -Most abundant chemical rock -Marine biochemical limestones form as coral reefs, coquina (broken shells), and chalk (microscopic organisms) -Inorganic limestones include travertine -Chert - name for a variety of rocks made of microcrystalline quartz -Flint -Inorganic Limestones -Crystalline limestone -Travertine -Evaporites: form as a body of water evaporates, forcing ions to precipitate -Rock salt (halite) -Gypsum -Sequence of precipitation from the evaporation of sea water -1st, Calcite - 1/3% -2nd, Gypsum - 3 1/2% -3rd, Halite - 78% Organic Sedimentary Rocks -Form from the accumulation of plant remains -Remains need to be buried quickly in an anoxic environment (no oxygen) -Types of Coal -Anthracite Coal - Highest carbon content (rare, only in Pennsylvania) -Lignite Coal - Low carbon content, lowest energy content -Bituminous - widest range of carbon content -Subbituminous Coal - dirty coal Continental Sedimentary Environments -Sedimentary Depositional Environment: the geographic setting where sediment is accumulating -Combination of geologic and environmental conditions determine what type of sediment will be deposited -We can study past environments by looking at sedimentary rocks -Strata: Name of sedimentary layers -Continental environments are dominated by erosion and deposition by streams/ rivers -Sediment deposited by stream channels -Large quantities of sediment deposited from floods -In some cold areas, glaciers are the dominant process -In arid regions (i.e. deserts) wind is the primary process -Clearly the sediment deposited in continental environments is dependent on climate -Size of sediment deposited is dependent on the energy of the erosion medium -Higher energy can transport larger grains -Lower energy can transport smaller grains -River environments will deposit sediment based on the energy of the water (how fast the river is flooding) -The sedimentary rocks formed from a river environment are usually red from oxidation -Usually have alternating layers of sandstone and shale from flow changes or river meandering -Rivers can produce asymmetrical ripple marks and cross-bedding sedimentary structures -Indicator of unidirectional flow in air or water -Cross-Bedding: Non horizontal layering within individual beds -Other indications of river (or lake) environments are mudcracks Marine Sedimentary Environments -Marine depositional environments are located in the oceans -Primarily where limestones come from -Separated into shallow marine and deep marine -Shallow marine environments border the continents -Reach depths of ~200 m (656ft) -Very wide at passive margins -Very narrow at active margins -Sediment deposited here is dependent on: -Distance from shore -Elevation of adjacent land -Water depth and temp -Climate -Shallow marine environments are usually coarse grained, such a sandstone -May have symmetrical ripple marks preserved -Warm, shallow, tropical waters produce limestone -Deep marine environments include the floors of the deep ocean -Far from continents (fine sediment) -Transition is the edge of the continental shelf -Black shales are typical of deep marine environment Transitional Sedimentary Environments -Transitional environments are along the shorelines and include beaches, tidal flats, lagoons, and river deltas (mouths) -High energy environments can produce sandstones -Low energy environments produce Fossils -Hard parts or impressions of organisms that have been preserved in the rock record -Continental and Marine -Metamorphics Metamorphism -Metamorphism: The solid-state change in composition and/or texture of a rock due to high temp and/or pressure -Temp ranges at which rocks form (picture, important) -Surface -> 200*C, Sediment converted to Sedimentary rock -200*C -> 700*C Increasing temp & pressure (rock form) -700*C -> 1200*C Partial melting -1200*C Complete melting -Heat: the most important agent in metamorphism -Causes recrystallization of new, stable minerals -Though mineralogy can change, overall chemical composition does not -Just re-arranges the elements already presents -Ex: If a shale undergoes metamorphism, the clay minerals will recrystallize as chlorite and mica -Minerals don't always have to change -2 Sources of Heat -Heat within the Earth, interior is extremely hot -Increase temp w/ depth -Heat from a magma chamber -The rock walls containing a magma chamber are heated by the magma -Pressure also increase with depth -Confining pressure is from the weight of overlying materials, equal in all directions -Differential stress is when pressure is stronger from some directions and not others -Usually happens along plate boundaries -Rocks act similar to putty or clay -Metamorphic rocks retain the chemical composition of the rocks they formed from (parent rock or protolith) -The mineral makeup of the parent rocks determines how much the rock will change during metamorphism -Parent rocks made mainly of the resistant mineral quartz will not change much -Parent rocks made of less resistant minerals (amphibole, olivine, etc) will alter significantly Metamorphic Textures -Texture: Refers to the size, shape, and arrangement of mineral grains -Foliation is any planar (flat) arrangement of minerals -Pressure squeezes minerals, causing them to form parallel alignment -Platy minerals like micas will rotate and become near parallel to each other -Prismatic/rectangular minerals (like amphiboles) and platy minerals tend to recrystallize parallel -Spherical grains will usually flatten -Under high-grade metamorphic conditions, minerals can become segregated into parallel bands -Foliation increases as metamorphic conditions increase (i.e. increase in heat and pressure) -Non-foliated textures also exist -No alignment or preferred orientation of minerals -Recrystallization does occur -No platy or elongated minerals to "flatten" -A limestone that gets metamorphosed is a marble -No foliation -A quartz sandstone that gets metamorphosed is a quartzite Metamorphic Environments -2 primary environments, although others exist -Contact Metamorphism -Rock surrounding a magma chamber become altered due to the intense heat -Usually produces non-foliated rocks -Regional Metamorphism -Associated with convergent zones and mountain building -Very large-scale -Produces foliate rocks -High Heat, High Pressure -by boundary -Gneiss in center, then Schist, Phyllite, and lastly slate Metamorphic Rocks -Common metamorphic rocks -Slate -Phyllite -Schist -Gneiss -Marble -Quartzite -Hornfels
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