Chapter 3 and Chapter 12
Chapter 3 and Chapter 12 EAS 2600
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This 7 page Class Notes was uploaded by Abigail Bruning on Sunday October 18, 2015. The Class Notes belongs to EAS 2600 at Georgia Institute of Technology taught by Andrew Vern Newman in Fall 2015. Since its upload, it has received 26 views. For similar materials see Earth Processes in Earth Sciences at Georgia Institute of Technology.
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Date Created: 10/18/15
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 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
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