Fall 2015 Block 2 Notes and Terms
Fall 2015 Block 2 Notes and Terms EAS 2600
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Date Created: 10/14/15
CH3 ROCKS AND MINERALS I What are minerals a Mineralogy study of the composition structure appearance stability occurrence and associations of minerals b Mineral naturally occurring solid crystalline substance usually inorganic with a specific chemical composition i Naturally occurring ii Solid crystalline structure solid with atoms that are arranged in an orderly repeating 3D array iii Usually inorganic exclude the organic materials that make up plant and animal bodies iv With a specific chemical composition composition is either fixed or varies within defined limits ie fixed ratio of atoms although varying number of atoms The Structure of Matter a Atoms i Nucleus protons and neutrons ii Electrons negligible mass iii Atomic number number of protons iv Atomic mass protons neutrons v Isotope same element with different numbers of neutrons vi Ion atom has a charge from either gaining or losing an electron o Cation positively charged 0 Anion negatively charged b Chemical compounds formed from i Electron sharing ii Electron transfer c Chemical Bonds i Ionic bonds transfer electrons strength decreases with distance and decreased electrical charge ii Covalent bonds share electrons stronger than ionic 0 Metallic bonds free electron sharing I The Formation of Minerals a Crystallization the atoms of a gas or liquid come together in the proper chemical proportions and in the proper arrangement to form a solid substance i Creates crystals ii When crystals grow over one another become a solid mass of particles grains b Minerals form from i Lowering temperature magma crystallizes into solid minerals when it cools water into ice ii Liquids evaporate leaving a precipitate c Polymorphs minerals with alternative structures formed from the same chemical element or compound d Density mass per unit volume gcm3 IV Classes of Rockforming Minerals a Silicates the most abundant class on the crust 95 i Silicate ion 4 oxygen ions around 1 silicon ion b NonSilicates i native elements pure not bound to another element ii Carbonates iii Oxides iv Evaporites v Sulfides vi Sulfates V Physical Properties of Minerals a Hardness how easy it is to scratch the surface i Moh s scale of hardness based on the ability of one mineral to scratch the other ii Depends on bond strength stronger bonds harder mineral b Cleavage tendency of a crystal to split along planar surfaces i the geometric pattern produced ii strong bonds poor cleavage poor bonds strong cleavage 0 number of planes pattern of cleavage 0 quality of surfaces ease of cleaving c Fracture tendency to break on irregular surfaces other than cleavage plane Luster the way the surface reflects light e Color i Streak color of the streak it leaves when scratched on a surface f Density i Specific gravity weight of a mineral divided by the weight on an equal volume of water g Crystal habit shape in which individual crystals grow VI Mineral Resources a Ores useful metallic minerals that can be mined for a profit Reserves identified mineralore deposits Hydrothermal solutions hot water solutions are formed around bodies of molten rock Veins sheetlike deposits of precipitated minerals in the fractures of a rock Disseminated deposits deposits of ore minerals that are scattered through volumes of rocks much larger than veins DPPPquot VII What are Rocks a Rock naturally occurring solid aggregate of minerals or nonmineral solid matter i Aggregate minerals are joined in a way that they retain their individual identity ii Texture sizes and shapes of a rock s minerals crystals or grains and the way they are put together b Igneous formed from the solidification of molten rock i Intrusive magma intrudes into unmelted rock masses deep in the crust ii Extrusive magmas that erupt on the surface as lava and cool rapidly c Sedimentary burial products of layers of loose particles sediment i Weathering all the processes that breakup and decay rocks ii Erosion processes that loosen soil and rock and move them downhill or downstream then deposited iii Siliciclastic sediments physically deposited particles running water wind ice iv Chemical sediments and biological sediments new chemical substances that form by precipitation v Lithification converts sediment into rock 0 Compaction squeezed together by weight of overlying sediments o Cementation minerals precipitate around deposited particles and bind them together vi Bedding formation of parallel layers of sediment as particles are deposited d Metamorphic formed by the transformation of preexisting solid rock under the influence of high temperatures and pressures i Regional metamorphism high pressures and temperatures extend over large regions where plates collide ii Contact metamorphism high temperatures are restricted to smaller areas magmatic intrusion VIII The Rock Cycle TERMS a Magma crystallization into igneous rock b Weathering and erosion c Deposition of weathered sediments d Deformation e Melting Anion Atomic mass Atomic number Bedding Biological sediment Carbonate Cation Chemical sediment Cleavage Color Contact metamorphism Covalent bond Crystal Crystal habit Crystallization Denshy Disseminated deposit Electron sharing Electron transfer Erosion Fracture Grain Hardness Hydrothermal solution Igneousrock Ion Ionic bond Isotope Lithification Luster Magma Metallic bond Metamorphic rock Mineral Moh s scale of hardness Ore Oxides Polymorph Precipitate Regional metamorphism Rock Rock cycle Sediment Sedimentary rock Silicate Siliciclastic sediment Specific gravity Streak Sulfate Sulfide Texture Trace element Vein Weathering CH4 IGNEOUS ROCKS I Overview a North American cordillera b Intrusive igneous rock has forced its way into the surrounding rock country rock and solidified without reaching earth s surface plutonic c Extrusive igneous rock rapid cooling at earth s surface glassy appearance volcanic i Lavas formed from flowing lavas ii Pyroclasts fragments of lava thrown high into the air 1 Volcanic ash extremely small fragments glass from a fine spray of magma 2 Volcanic bombs larger pieces that cool in the air How They Differ From One Another a Texture linked to rate and place of cooling slow cooling allows for orderly patterns to form crystals i Coarsegrained slow rate of cooling larger crystals 2 Diorite ii Finegrained fast rate of cooling 2 Basalt iii Glassy no crystals cools extremely fast 2 obsidian iv Porphyritic two crystal sizes suggests two rates of cooling 2 Granite b Chemical and Mineral composition i Felsic rocks poor in iron and magnesium and rich in silica light in color feldspar silica low melting point 2 Granite almost entirely lightcolored silicates 2 rhyolite ii Intermediate igneous rocks neither rich nor poor in silica 2 Andesite diorite iii Mafic rocks rich in iron and magnesium and poor in silica dark in color magnesium iron high melting point 2 Basalt gabbro intrusive form of basalt substantial dark silicate materials iv Ultramafic rocks primarily mafic minerals 2 Peridotite Intrusive to Extrusive Granite 9 rhyolite Diorite 9 andesite Gabbro 9 basalt Hi How Magmas Form a Rock melting depends on i Temperature 1 Partial melting minerals that compose rocks melt at different temperatures ii Pressure higher pressures creates higher melting temperatures 1 Decompression melting when material rises and the pressure on it decreases solid rock melts spontaneously without an increase in temperature greatest volume of magma on Earth iii Water lowers the melting point 1 Fluid induced melting melting of rock due to water lowering its melting point b Magma chambers large pools of molten rock that form in the lithosphere as rising magmas melt and push aside surrounding solid rock IV Magmatic Differentiation a Magmatic differentiation rocks of varying composition can come from a uniform parent magma i Due to different minerals crystallizing at different temperatures b Fractional crystallization when crystals form in a cooling magma and separate from the remaining liquid rock i Bowen s reaction series defines the order of mineral crystallization by melting temperature V Forms of Igneous Intrusion a Plutons large igneous bodies formed deep in the earth s crust i Batholiths largest plutons great irregular masses of coarsegrained igneous rock often form the cores of mountains Sierra Nevada mountains ii Stocks smaller plutons o Discordant intrusions cut across the layers of country rock they intrude b Sills sheetlike body formed by magma injected between parallel layers of country rock 0 Concordant intrusions lie parallel to the country rock layers Dikes sheetlike body that cuts through the layers of country rock 0 Discordant intrusion c Veins minerals within a rock fracture that are foreign to the country rock i pegmatites VI Processes and Plate Tectonics a Spreading centers divergent i Decompression melting material rises to less pressure environment ii Mafic intrusives and extrusives low viscosity no explosive eruptions iii Ophiolite suites assemblages of deepsea sediment submarine basaltic lava and magic igneous intrusions fragments of oceanic lithosphere that surface due to seafloor spreading b Subduction zones convergent i Oceanocean convergence 1 Volcanic islands mafic to intermediate rock moderate viscosity some explosive eruptions 2 Fluidinduced melting water from subducted plate causes rock to melt ii Oceancontinent convergence 1 Continental plate mafic to felsic intrusives and extrusives viscosity medium to high many explosive eruptions c Mantle plumes i Decompression melting within plates d Hot spots i Ultramafic to mafic low viscosity few explosive eruptions TERMS o Extrusive igneous rock 0 Felsic rock 0 Andesite o Fluidinduced melting o Basalt 0 Fractional crystallization o Bathollth G bb o a ro o Concordantintrusion G t o ranIe 0 Country rock 0 Decompression melting o Dike o Diorite 0 Intermediate igneous rock 0 Intrusive igneous rock 0 Lava 0 Mafic rock 0 DiscordantIntruSIon Magma chamber Magmatic differentiation Ophiolite suite Partial melting Pegmatite Pluton Pyroclasts Rhyolite Sill Stock Ultramafic rock Vein Viscosity Volcanic ash Volcanic bomb Ch5 Sedimentary Rocks I Surface Processes of the Rock Cycle a Sediments become rocks i weathering 9 erosion 9 deposited in a sink 9 buried compacted and lithified through diagenisis 9 becomes a rock b Weathering and erosion the source of sediments i Weathering general process in which rocks are broken down creating sediment 1 Physical weathering due to mechanical processes that don t alter the chemical composition freezethaw tree roots fault abrasion 2 Chemical weathering processes where rocks are chemically altered or dissolved ii Siliciclastic sediments formed from silicate minerals in rocks iii Chemical sediments dissolved ions and molecules that accumulate and then precipitate to form chemical sediments gypsum and halite 1 Biological sediments result of mineral precipitation by organisms plankton crustaceans c Transportation and deposition i Fluvial moved by water ii Alluvial moved by gravity iii Aeolian moved by wind iv Glacial moved by glaciers v Biological moved by creatures vi Strength of current affects 1 Size of sediment abrasion through transport larger particles harder to move 2 Sorting different sediments being deposited at different rates 3 Rounding of the sediment smooth sediment through abrasion farther it moves smoother it becomes Burial and Diagenesis Sediment to Rock a Burial covering of sediment within a sink deep seafloor is the ultimate basin final resting place b Diagenisis physical and chemical changes from the high temperatures and pressures of being buried under sediments i Cementation when minerals precipitate in the pores between the sediment particles and bind them together decreases porosity calcites silica iron oxides ii Compaction decrease in volume and porosity iii Final step is lithification hardening of soft sediment into rock I Sedimentary Basins a Sedimentary basin combination of sedimentation and subsidence broad area of crust sinks i Thermal subsidence basin cooling of lithosphere causes depression in the crust above 1 Continental shelf sediment builds up near continents ii Rift basin deep narrow and long basin at a divergent boundary eventually becomes a lake place of deposition iii Flexural basin at a convergent boundary the weight of the overriding plate causes the underlying plate to bend down IV Sedimentary Environments all sinks but not necessarily basins a Continental siliciclastic lakes inland seas deserts glaciers b Shoreline siliciclastic chemical and biological river deltas beach tidal flats c Marine chemical and biological deep sea continental shelf continental slope organic reef d Siliciclastic vs Chemical sedimentary environments V VI TERMS 0903 Bedding sequence i Chemical and biological sediments carbonate deposits siliceous environments evaporite environments salty places Sedimentary Structures a Bedding stratification i Crossbedding wind or water erosion on one side then deposited on the other side ii Gradedbedding wellsorted bedding further from source only things of certain size make it to that point iii Ripples and ripple marks surface features showing wave motion iv Bioturbation structures biological activity moves sediment and disrupts original environment v Bedding sequences stacked layers of rock with different structures in each layer strata bedding planes fossils 9 powerful time indicators and information about past environments Classification of Siliciclastic Sediment Lithic similar composition to source Arkose feldspar and quartz Quartz arenite quartz sand Graywacke quartz and clays Detrital rocks produced by mechanical erosion solid particles classified by particle size Finegrained 9 mediumgrained 9 coarsegrained i Shale most abundant grains and clay mediumgrained ii Sandstone lithified sand finegrained Chemical rocks derived from material in solution and precipitates Carbonates or evaporates marine or nonmarine i Limestone carbonate sediments organic reef development rapid limestone formation due to biological activity Bahamas ii Coal plant origin diagenisis of wetland vegetation iii Evaporites salt gypsum o Sedimentary structure 0 Siliciclastic sediments o Silt Bioclastic sediment Biological sediment o Sorting o Subsidence Bioturbation Carbonate rock sediment o Terrigenous sediment 0 Thermal subsidence basin Cementation Chemical sediment Chemical weathering Compaction Continental shelf Crossbedding Diagenisis Evaporite rock sediment Flexural basin Lithification Physical weathering Porosity Rift basin Ripple Sedimentary basin Sedimentary environment CH6 METAMORPHIC ROCKS I Causes of Metamorphism mainly in the deep crust alteration of mineral composition and texture composition happens in solid state no melting Degrees a Lowgrade somewhat similar to original shale becomes slate Highgrade obliteration of original features Index minerals reflect pressure and temperature conditions giving grade b Temperature C d Heat breaks chemical bonds and causes recrystallization at new temperatures Geothermal gradient temperature increases with depth Pressure stress ii Fluids i ii Confining pressure general force applied equally in all directions material added above it 1 Geobarometers indicate pressure because minerals are stable under certain pressures Directed differential pressure force exerted in a particular direction tectonic collision Hydrothermal fluids accelerate metamorphism Metasomatism change in a rock s composition by fluid transport into or out of the rock II Types of Metamorphism Regional metamorphism large areas of the crust with both high temperatures and high pressures as opposed to localized transformation from igneous intrusions Contact metamorphism thin layer of country rock around an igneous intrusion heat induced Highpressure metamorphism along linear belts of volcanic arcs produced by continentcontinent collision creating high pressures Seafloor metamorphism midocean ridges where intruding magma drives seawater circulation through extruded basalts Burial metamorphism transforms sedimentary rock through increasing pressure and temperature Shock metamorphism heat and shock waves of a meteorite impact III Metamorphic Textures Foliation parallel cleavage due to directed pressure 9 creates foliated rocks a e f a Increasing grade and crystal size i ii iii iv v Slates fine grained planar splits easily PhyHHes Schist strongly foliated grains Gneiss strong segregation of silicate minerals Migmatite b Granoblastic rocks or nonfoliated composed mainly of crystals that grow in equant shapes Increasing grade and crystal size C v vi Hornfels Quartzites Marbles limestone host rock large interlocking calcite crystals Greenstones Amphibolites Granulite Porphyroblasts large crystals found in rocks formed from contact and regional metamorphism Stable over a broad range of pressures and temperatures so stay constant while other minerals are recrystallizing IV Regional Metamorphism and Metamorphic Grade Mineral lsograds boundary of grade changes reflected by index minerals b Grade and Parent rocks a i Zeolite ii Greenschists and blue schists c Metamorphic facies groupings of rocks of various minerals formed under particular conditions i different kinds of metamorphic rocks of the same grade form from different parent rocks ii different kinds of metamorphic rocks of different grades form from same parent rocks V Plate Tectonics and Metamorphism a Retrograde path vs prograde paths indicate rockregion s history of plate s i Prograde burial causes increase pressure and temperature ii Retrograde exhumation causes decrease in pressure and temperature b Plates i Continental interiors ii Divergent plate boundaries iii Convergent plate boundaries 1 Oceancontinent a Melange 2 Continentcontinent a Suture iv Transform faults c PressureTemperature paths i Exhumed transported back to the surface ii PT path history of changing pressure and temperature shown in its texture and mineralogy TERMS Amphibolite Burial metamorphism Contact metamorphism Exhume Foliation foliated rock Granoblastic rock Highpressure metamorphism Metamorphic facies Metasomatism Migmatite PT path Quartzite Regional metamorphism Seafloor metamorphism Shock metamorphism Stress CH8 CLOCKS IN ROCKS I Reconstructing Geologic History from the Stratigraphic Record a Uniformitarianism quotpresent is the key to the past b Absolute age number of years elapsed from that event until now c Relative age earlier or later than another event d Stratigraphy the study of strata layers in rocks i Principle of original horizontality sediments are deposited under the influence of gravity ii Principle of superposition each layer is younger than the one beneath it 1 Stratigraphic succession chronologically ordered set of strata Gaps can occur due to droughtfloodserosion Can t compare over large distances Relative Dating a Principle of original horizontality b Law of superposition c Cross Cutting Relationships any geologic feature that cuts across another feature must be younger than the feature it crosses d Inclusions rock or sediment that includes another rock in its body must be younger the rock trapped in another rock must me older e Unconformities i Nonconformity younger sedimentary rock overlying older metamorphic or igneous rocks ii Disconformity missing time between horizontal layers of sedimentary layers iii Angular unconformity missing time between sedimentary layers that are not parallel to each other Grand Zion and Bryce Canyons 9 is a near continuous sedimentary section III Fossils a Stratigraphic ordering of fossils i Principle of faunal succession layers contain fossils of definite sequence determinable order 1 Can be used to match layers of separate locations 2 Index fossil widespread geographically existed for short range of geologic time ii Paleontology study of past life forms and ecosystems I Petrified cavities and pores are filled with precipitated mineral matter ii Mineral replacement cell material is removed and replaced with mineral matter iii Mold living structure is dissolved leaving an imprint iv Cast a mold filled with mineral matter c Conditions i Rapid burial can t be moved eaten altered before being buried ii Possession of hard parts can t be squished and have shape altered due to burial d Preservation carbonization organic matter leaves thin residue of carbon impression preservation in amber e Indirect fossils i Trace fossils imprints left behind as signs of life coprolites and gastroliths IV Radioactivity a Isotope atom with a different number of protons than neutrons b Radioactive decay parent unstable isotope decays and emits daughter products c Radiometric dating the ratio of parent to daughter gives absolute age i Halflife time for half of the radioactive nuclei to decay 50 parent and 50 daughter V Other Stratigraphy a Sequence stratigraphy history of an environment from relative deposition of material in sequences often due to climate changes b Paleomagnetic stratigraphy use remnant magnetism to recreate history VI Geologic time scales a Difficulties i Not all rocks are datable sedimentary ages are rarely reliable ii Materials are often used to bracket events and arrive at ages b Eon gt era gt period gt epoch boundaries marked by significant events usually mass extinctions i Hadean fiery oldest ii Archaen ancient iii Proterozoic quotearlier life iv Phanerozoic quotwith life 1 Paleozoic quotancient life 2 Mesozoic quotmiddle life 3 Cenozoic quotrecent life a Paleogene b Neogene c Quaternary i Pleistocene ii Holocene ii Anthropocene coalpowered steam engine 1780 TERMS 0 Period ESECh o Principle of superposition Era 0 Relative age o Stratigraphic succession 0 Geologic tIme scale Stratigraphy o Halflife o Unconformity o IsotopchatIng 0 Mass extinction CH 12 VOLCANOES I Volcanoes as Geosystems a Process 1 Magma originates in the asthenosphere 2 Rises through the lithosphere to form a crustal magma chamber 3 Lava erupts through a central vent 4 Accumulating in the surface to form a volcano b Importance i Windows into the interior of the earth ii Plate tectonic processes and mantle convection iii Produces and perturbs atmosphere and hydrosphere iv Produce rich agricultural terrains c Conduit pipe that carries gasrich magma to the surface d Vent the opening on the surface II Plate Boundaries a Divergent boundaries most of world s volcanism i Spreading centers oceanic ridges and rift valleys land ii Basaltic lava from mantle fissure eruptions iii Caused by decompression melting b OceanOcean convergence i Buoyancy allows magma to drip up ii Forms island chains on hanging wall slab iii Source of new continental crust c OceanContinental convergence i Buoyancy allows magma to drip up ii Long residency in thicker continental crust loses some volatiles more explosive iii Forms new continental crust on surface and below ContinentContinent convergence little to no volcanism e Hot Spot Volcanism i Heated rock deep within the mantle forms a magmatic pipe to the surface ii Can occur anywhere source is not well understood iii Creates longlived hot spot chain plate motion causes the chain to form Hawaii iv Iceland hotspot on a spreading center v LIPS Large Igneous Provinces extremely massive lava flows 1 Mantle plume rises to the lithosphere 2 Material reaches the surface creating a volcano 3 Creates plume tail that stays below moving plates above III Lavas Volcanic Deposits a Basaltic lava along midocean ridges hot spots within plates and continental rift vaHeys i When hot fluid magmas fill up a volcano and overflow rarely explosive more fluid ii Pahoehoe lava that spreads in sheets and a thin glassy elastic skin congeals on its surface as it cools iii Aa lava that looks like clumps of moist freshly plowed earth b Andesitic lava volcanic mountain belts above subduction zones Andes in South America i Lower temperatures silica content is higher flow more slowly lumpy ii Can plug the central vent and trap gasses explosive Mt St Helens c Rhyolitic lavas d Pyroclastic flows hot ash and gases in a glowing cloud that rolls downhill at high speeds i Volcanic bombs fragments ejected as blobs of lava that cool in flight or chunks torn loose from previously solidified volcanic rock IV Types of Eruptions a Central eruptions discharge lava or pyroclasts from a central vent atop a pipelike formation i Shield volcanoes lava cone with relatively gentle slopes ii Cinder cones steeper sloping iii Stratovolcanoes alternate between lava and pyroclasts most violent 1 Nuee ardente fiery pyroclastic flow made of hot gases infused with ash 2 Lahars torrential flow of wet volcanic debris rainfall glaciers river etc b Other forms i Craters bowlshaped at the summit of a volcano ii Calderas when a volcano collapses on itself leaving a basinshaped depression 1 Crater Lake Oregon Long Valley Caldera Santorini Caldera iii Volcanic domes so viscous they barely flow of lava slowly squeezed out iv Diatremes after an explosion the leftover volcanic brecca in the pipe v Fissure eruptions long cracks in the earth s surface midocean ridges vi Volcanic pipes short conduits that connect a magma chamber to the surface vii Volcanic necks resistant vents left standing after erosion has removed a cone viii Pluton large magmatic features solidified at depth ix Batholith massive silicic body x Intrusions 1 Sill horizontal 2 Dike dipping diagonal V Eruptions a Depend on i Viscosity resistance of material to flow low viscosity flows easily high resists flow 1 Temperature higher temperature low viscosity 2 Volatile content provide the force to extrude lava how easily for gas to escape from magma lower viscosity 3 Silica content high silica content lower melting temperature high silica content high viscosity VI Global Pattern a Ring of fire edges of the pacific plate b Mainly plate boundaries and hot spots TERMS o Andesitic lava o Basaltic lava o Caldera o Cinder cone 0 Crater o Fissure eruption 0 Hot spot 0 Lahar 0 Large igneous province 0 Mantle plume o Pyroclastic flow 0 Shield volcano o Stratovolcano
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