Chapter 4 and Chapter 5
Chapter 4 and Chapter 5 EAS 2600
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EAS 2600 A
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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 18 views. For similar materials see Earth Processes in Earth Sciences at Georgia Institute of Technology.
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What is Karma?
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Date Created: 10/18/15
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 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