Study Guide 80203 - GEOL 1010-003
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This 45 page Study Guide was uploaded by Alex Casale on Wednesday October 7, 2015. The Study Guide belongs to 80203 - GEOL 1010-003 at Clemson University taught by Mine Dogan in Summer 2015. Since its upload, it has received 180 views. For similar materials see Physical Geology in Geology at Clemson University.
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Date Created: 10/07/15
Chapter 5 Weathering amp Soil 10615 1011 PM Weathering The physical breakdown and chemical alteration of rock at or near Earth s surface 0 Takes thousands of years 0 Temperature is extremely important 0 2 Categories of Weathering Mechanical and Chemical Mechanical Weathering Breaking of rocks into smaller pieces 0 Have an increased Surface Area 0 Frost Wedqinq Water will work its way into cracks of rocks the water will freeze and expand leading to the rocks fragmenting Frost edging o Sheeting exfoliation of igneous and metamorphic rocks When large rocks are exposed to erosion concrete slabs begin to break loose Confining pressure leads the rocks to crack Cracks revealed through temperature changes Never ending process until it consumes the entire material a overburden eroding 9 pressure reduced overburden s 4gt A small crack in a rock lls Asthewaterfreeezes with water during the daytime completely its 9 growth If the 3999 thaws the quot33 quot 535 As the water begins to freeze exerts an OUtWBrd forte on me resug39n hmate W1quot 310m at night it starts at the top the sides ofthe crack 9 quotat 390 398 9W sealing the crack increasing the size of the Wder and deeper because 0f crack by a maximum of 9 3 9 expans on DEW 0r rainfall on the rock surface can refill the crack Again the crack expands by as much as 9 Continuedfreezing and thawing particularly with the daily addition of water to keep the crack full eyentually does significant fracturing ofthe rock arge The process begins again this time with a larger initial crack 0 Biological Activity disintegration resulting from plants and animals Extremely fast compared others Chemical Weathering Breaks down rock components and the internal structures of minerals 9 The complex process that alter the internal structures of minerals by removing andor adding elements 0 Weakens the outer portion of some rocks which makes them more vulnerable to being broken by mechanical weathering processes 0 Optimum environment is a combination of warm temperatures and abundant moisture Most important agent involved in chemical weathering is water responsible for transport of ions and molecules involved in chemical processes 0 1 Dissolvinq aided by small amount of acid in the water Soluble ions are retained in the underground water supply Example Iron nail is found in most soil it has a coating of rust iron oxide the nail can be so weak that it can break by the poke of a toothpick o 2 Oxidizinq any chemical reaction in which a compound or radical loses electrons Important in decomposing ferromagnesian minerals Major Processes of Chemical Weathering 0 Example how granite weathers o Chemically attacks by carbonic acid 0 Hydrogen ion attacks and replaces other positive ions 0 Most abundant product is clay minerals Weathering amp Characteristics that can Affect it o Alterations caused by chemical weathering o Decomposition of unstable minerals 0 Generation or retention of materials that are stable 0 Physical changes such as the rounding of corners or edges spheroidal weathering 0 Advanced mechanical weathering aids chemical weathering by increasing the surface area 0 Other factors affecting weathering 0 Rock characteristics Rock containing calcite marble and limestone readily dissolve in weakly acidic solutions Silicate minerals weather in the same order as their order of crystallization Example Headstones show weathering within a short amount of time Examine the inscriptions on the stone Precise writing 9 blurry writing 0 Climate Temperature and moisture are the most crucial factors Chemical weathering is most effective in areas of warm moist climates 0 Differential Weathering Masses of rock do not weather uniformly because of regional and local factors Results in many unusual and spectacular rock formations and landforms More resistant rock protrudes as ridges or pinnacles or steeper cliffs m 2 o A combination of mineral and organic water matter and air 0 One of the most indispensable resources Regoith is rock and mineral fragments produced by weathering that supports the growth of plants Good Soil 0 25 air 0 25 water 0 45 mineral matter 0 5 organic matter 0 Factors Controlling Soil Formation Parent material time climate plants and animals slope 1 Parent Material 0 The source of the weathered mineral matter from which soils develop major influence new forming soil 0 Parent Material influences soil in two ways 1 The type of parent material will affect the rates of weathering leading to the rate of soil formation a Soil development will progress more rapidly on transported soils because that material is already partly weathered 2 The chemical makeup of the parent material will affect the soil s fertility 0 Residual soil Parent material is the underlying bedrock o Transported soil Forms in place on parent material that have been carried rom elsewhere and deposited 2 m 0 Important in all geologic processes 0 The nature of the soil is strongly influenced by the length of time processes have been operating 0 The longer a soil has been forming the thicker it becomes and the less it resembles the parent material 0 3 Climate 0 Most influential control of soil formation 0 Key factors are temperature and precipitation 0 Variations in temperature and precipitation determine whether chemical or mechanical weathering will dominate 0 Example Hot wet climate will produce a thick layer of chemically weathered soil in the same amount of time that a cold dry climate produces a thin mantle of mechanically weathered debris o The amount of precipitation influences leaching Leaching is the process which various materials are removed from soil by percolating filtering waters 0 4 Plants and Animals 0 Plants and animals influence the soil s physical and chemical properties 0 Plants and animals provide organic matter to the soil Primary source of organic matter in soil are plants 0 5 Topography Slopes 0 Length and Steepness of the slopes have a significant impact on the amount of erosion and the water content of soil Steep slopes often have poorly developed soils Optimum terrain is a flattoundulating upland surface Perfect soil is produced on smooth almost flat surfaces Slope Orientation is the direction the slope is facing This is another thing to consider when looking at soil The Soil Profile 0 Soil forming processes operate from the surface downward Vertical differences are called horizons which are zones or layers of soil 0 O horizon organic matter 0 A horizon organic and mineral matter 0 E horizon little organic matter 0 B horizon zone of accumulation C horizon partially altered parent material 0 The O A E and B horizons together are called the solum or true III OOOO soi O horizon Loose and partly decayed organic matter A horizon Mineral matter mixed with some humus E horizon t Light celored 3quot q mineral particles w y Zone of eluviation q N 4 l39 r s o and leaching O 1 Bhon39zon 39 Accumulation of clay transported from above C hon zon Partially altered parent material Unweathered parent material Soil Classification 0 Soil Types Groups consist of items that have certain important characteristics in common 0 Soil Taxonomy Includes 6 hierarchical categories of classification ranging from order broadest to series most specific Useful for agricultural and related landuse purposes The Impact of Human Activity on Soils Soils form very slowly it must be thought of as a nonrenewable resource 0 Soils can be damaged or destroyed by careless activities 0 The agricultural productivity of soils can be improved through fertilization and irrigation Clearing the Tropical Rain Forest 0 Tropical forests are cleared for logging and agricultural use 0 Soils in tropical forests are poor in nutrients and unsuitable for agriculture 0 Most of the nutrients in tropical rain forests are found in the trees 0 Soil Erosion 0 Natural process in the rock cycle 0 Erosion rates are dependent on climate slope and type of vegetation o Deforestation and Farming practices can enhance soil erosion Weathering and Ore Deposits o Weathering creates deposits by concentrating metals into economically valuable concentrations secondary enrichment o Bauxite principal ore of aluminum Forms in rainy tropical climates from chemical weathering and the removal of undesirable elements by leaching o Other deposits Weathering processes concentrate metals that are deposited through lowgrade primary ore n Copper and silver i 2 coarse 10615 1011 PM 15 2 mm mallllm Sand I I 55 mm fine Silt l MUd 4134 mm quot I Mud is a mixture of silt and clay sized partic es I gIUII no I39llII W39UDIIIIIUIIIIui The formation of sediment processes that breakup and dissolve rock MechanicalPhysical break and crack Chemical dissolve transform corrode oxidize Types of Sedimentary Rocks 0 1 Detrital clastic cemented together fragments and grains of preexisting rock Clast from klastos 2 Chemical nonclastic Minerals that precipitate directly from solution 0 3 Bio chemical made from shells of organisms 4 Organic Carbon rich relicts of plants 1 Detrital Clastic Sedimentary Rocks Cemented together fragments and grains of preexisting rock Clast from klastos Starts with mechanical aka physical weathering Breaks rocks into smaller grains or chunks Detritus and Clasts the weathered pieces 0 COARSE MEDIUM FINE are key terms to be familiar with Weathering breaks down solid rock into smaller pieces Erosion removes clasts from source and transports them Deposition occurs when the rock can no longer be carried and are therefore left behind deposited Steep narrow slopes and fast flowing water from the top of the mountain to the bottom is needed to transfer large materials Wind can transfer small particles like sand and clay iClicker Question The Clasts in this stream are all gravel size or largerVVhy 0 00000 The stream has carried away all the smaller particles high energy The source of these rocks must be near by short transport distance Depositional energy of the environmental will determine grain size Fast pace due to steep slope high energy Coarse large grained Moderate pace due to moderate slope medium grained Slow pace hardly any slope low energy fine grained Course grains fall out faster than fine grains Slope steepness influences speed of transport Transport seed influences grain size Steep grade 9 fast water 9 deposits only large grains Gentle grade 9 slow water 9 deposits fine grain size Reflecting transport processes 9 well sorted materials more likely for long transport distances Well sorted sand all grain sizes are mostly equal Deltas stream into water body Beach faces wave action Wind blown sediments Poorly Sorted Sand obvious different grain sizes Sharp change in stream gradient Rock falls talus slopes Glaciers vw N f l 53 U Particle sizes for detrital rocks 4 r 39I n quotx x l 9 Particle Size Classification for Detrital Rocks 39 but Size Range millimeters gt256 64 256 4 64 2 4 116 2 1256 116 lt1256 Particle Name Common Sediment Name Detrital Rock Boulder Cobble Gravel Conglomerate or breccia mty Pebble Granule Sand Sand Sandstone Silt Mud Shale mudstone or siltstone Clay 10 20 30 40 50 6O Wm Copyright 2009 Pearson Prentice Hall Inc How do they form O O O Weathering breaks down solid rock into smaller pieces Erosion removes clasts from source and transports them Deposition occurs when the rock can no longer be carried and are therefore left behind deposited Steep narrow slopes and fast flowing water from the top of the mountain to the bottom is needed to transfer large materials Moderate nlgn energy The source of these rocks must be near by short transport distance 0 Clastic Sedimentary Rocks Grain Size 0 Depositional energy of the environmental will determine grain snze 0 Fast pace due to steep slope high energy Coarse large grained Moderate pace due to moderate slope medium grained Slow pace hardly any slope low energy fine grained Course grains fall out faster than fine grains Slope steepness influences speed of transport Transport seed influences grain size Steep grade 9 fast water 9 deposits only large grains Gentle grade 9 slow water 9 deposits fine grain size 00000 IN 39 IO lm In I Sedimentary Rocks Sorting o Reflecting transport processes 9 well sorted materials more likely for long transport distances 0 Well sorted sand all grain sizes are mostly equal Deltas stream into water body Beach faces wave action Wind blown sediments o Poorly Sorted Sand obvious different grain sizes Sharp change in stream gradient Rock falls talus slopes Wellsorted sand lnr Poorly sorted sand i I h r Clastic Sedimentary Rocks Grain Shape O 0 Short Distance from original source rugged shape large Moderate Distance from original source smoother shape but still rough medium size Long Distance from original source perfectly round and smooth small Know how grain size shape and sorting varies with maturity distance of transport Very poorly sorted 9 poorly sorted 9 moderately sorted 9 well sorted 9 very well sorted Angular rugged 9 subangular rugged by somewhat smoothed out 9 subrounded between smooth and angular 9 rounded completely smooth UISIanCE 1 transport Short Moderate Long 0 gt Larger Smaller more angular more rounded A O o Clastic Sedimentary Rocks Digenesis o Recrystallization development of more stable minerals from less stable ones 0 Lithification unconsolidated sediments are transformed CompactionDewaterinq completely underwater n More grains on top of each other Cementation by calcite silica and iron oxide The cement fills spaces between grains See individual grains a Question How is this different with igneous rocks the crystals of igneous rocks grow into each other You cannot see the individual grains 0 Clastic Sedimentary Rocks Examples 0 SHALE Silt and claysized particles Form from the gradual settling of sediments in quiet nonturbulent environments Sediments form in thin layers that are called laminae Has fissility meaning the rock can be split into thin layers Crumbles easily and tends to form gentle slopes Most abundant sedimentary rock 0 SANDSTONE Sandsized particles Forms in a variety of environments Second most abundant sedimentary rock Quartz is the most abundant mineral Quartz sandstone in predominately composed of quartz Arkose sandstone contains appreciable quantities of edspar Greywacke contains rock fragments and matrix in attrition to quartz and sandstone o CONGLOMERATE and BRECCIA Conglomerate consists of rounded gravelsized sediments Breccia consist of angular gravelsized sediments n Poorly sorted Sedimentary Rock Recap Sediments and sedimentary rocks cover approximately 75 of the earth They comprise about 5 by volume of Earth s outer 10 miles Contain evidence of past environments Sedimentary rocks are an important resource 0 Coal oil and other fossil fuels 0 Groundwater resources Sedimentary rocks are products of mechanical and chemical weathering Sediments and soluble constituents are typically transported downslope by gravity The sediments are then deposited and subsequently buried As deposition continues the sediments are lithified into sedimentary rocks There are 4 different types of Sedimentary Rocks o Detrital 0 Chemical 0 Biochemical 0 Organic Clastic Sedimentary Rock Recap Clastic detrital sedimentary rocks form from sediments that have been weathered and transported The chief constituents of detrital rocks include clay minerals quartz feldspars and micas 0 Particle size is used to distinguish among the various rock types 2 Chemical NonClastic Sedimentary Rocks 0 Form from precipitated material that was once in solution Precipitation of material occurs by 0 Inorganic processes such as evaporation 0 Organic processed from waterdwelling organisms form biochemical sedimentary rocks 0 Chemical Sedimentary Rocks Examples 0 LIMESTONE Most abundant chemical sedimentary rock Mainly composed of the mineral calcite Can form from inorganic and biochemical origins Inorganic limestone forms when chemical changes increase the calcium carbonate content of the water until it precipitates n Travertine is a type of limestone found in caves It s precipitated when the water in the cave loses carbon calcium n Ooitic limestone is composed of small spherical grains called ooids Coquina is composed of cemented fragments of shell material Chalk is composed of hard parts of microscopic marine organisms o DOLOSTONE DOLOMITE Similar to limestone but contains magnesium Origin of dolostone is unclear Significant quantities of dolostone are created when magnesiumrich waters circulate through limestones o CHERT Composed of microcrystalline quartz Forms when dissolved silica precipitates Flint jasper and agate are varieties of Chert o EVAPORITES Form when restricted seaways become oversaturated and salt deposition starts Rock salt and rock gypsum are two common evaporites Occasionally evaporites form on salt flats when dissolved materials are precipitated as white crust on the ground 3 Biochemical 0 Biochemical limestone originates from the shells of marine organisms 0 Large quantities of marine limestone are formed from corals o Corals secrete a calcium carbonate skeleton and create reefs o Australia s Great Barrier Reef is the largest coral reef on Earth 0 Coquina a type of limestone is composed of cemented fragments of shell material 0 Chalk a type of limestoneO is composed of the hard parts of microscopic marine organisms 4 Organic Sedimentary Rocks Coal 0 Organic sedimentary rocks form from the carbonrich remains of organisms Occasionally plant structures leaves bark and wood identifiable in coal 0 Stages of Coal Formation o 1 Accumulation of plant remains o 2 Formation of peat o 3 Formation of lignite and bituminous coal 0 Formation of anthracite coal 3quotquot WWWquot l g 39Tln l quot 39 quot M I39 i 3939lx IIP39NUS a 392 39 d Diagenesis and Lithification Many changes occur to sediment after it is deposited o Diagenesis chemical physical and biological changes that take place after sediments are deposited and buried Occurs within the upper few kilometers of earth s crust Examples Recrystallization of more stable minerals from less stable ones for example aragonite to calcite o Lithi cation Unconsolidated sediments are transformed into sedimentary rocks Compaction as sediments are buried the weight of the overlying material compresses the deeper sediments Cementation involves the crystallization of minerals among the individual sediment grains Water lled pore spaces Pressure 1 i ll 1 2 il l 5 v v J Compacted loosely packed sediment clay size particles sedimentary rock magni ed Circulation ol mineral bearing groundwater loosely packed Gradually the cementing sand or gravel material fills much of the size particles pore space and glues magni ed the grains together Classification of Sedimentary Rocks Two Major Groups 0 1 Detrital Has clastic texture composed of discrete fragments cemented together 0 2 ChemicalOrganic Has nonclastic or crystalline texture where the minerals form patterns of interlocked crystals l W h l j M Rounded pencles Cum move than m 3 i393jr luh 116102mm m 1116 to 1256 mm M M less lhan 1256 mm labunda t el39jsw IS yawn the rock 5 134sz Arhcse Past Environments An environment of deposition or a sedimentary environment is a geographic setting where sediment is accumulating Determines the nature of the sediment that is accumulating grain size grain shape etc 3 broad categories of sedimentary environments 0 Continental 0 Marine o Transitional Continental Environments Dominated by stream erosion and deposition 0 At the top of the stream large sediment with jagged edges 0 Bottom of the stream smaller sizes with more rounded edges fine sand clay slit Glacial 0 Deposits typically unsorted mixtures of sediments that range from clay to boulder size 0 Wind eolian o Wellsorted fine sediements Marine Environments 0 Shallow 200m 0 Boarders of worlds continents o Receives huge quantities of terrestrial sediments 0 Warm seas with minimal terrestrial sediments have carbonaterich muds o Turbidity current drop off from shelf to deep sea You see bigger chunks here because its a drastic drop off Everywhere else you see fine grain in the deep sea 0 Deep ltarine seaward of continental shelves 0 Primarily fine sediments that accumulate on the ocean floor 0 Turbidity currents are the exception Transitional Environments Transition zone between marine and continental Examples shoreline beaches tidal flats lagoons deltas o deltas Low energy like swamp Very well sorted Sedimentary Facies The volume of sediment is all the same 0 Different sediments often accumulate in adjacent environments 0 Each unit possesses a distinctive set of characteristics reflecting the conditions of a particular environment 0 Transitions between types are typically gradual Sedimentary Structures 0 Provide info useful in interpretation of Earth s history 0 Stratabeds the single most common and characteristic feature of sedimentary rocks Every stratum is unique 0 Types of Sedimentary Structures 0 Bedding planes what separates the strata 0 Cross Bedding A structure in which relatively thin layers are inclined at an angle to the main bedding Formed by currents of wind or water 0 Graded Beds The particles within a single sedimentary later gradually change from coarse at the bottom to fine at the top Rapid deposition from water containing sediment of varying sizes 0 Ripple Marks small waves of sand that develop on the surface of a sediment layer through the action of moving water or air 0 Mud Cracks indicate that the sediment in which they were formed was alternately wet and dry 0 Fossils the remains or traces of prehistoric life 0 iClicker Question If you found the following sequence of rocks what does that tell you about their depositional environment Soil 9 Sandstone 9 Shale 9 Limestone n The environment changed from terrestrial to marine overtime Transgressive Sequence 0 Sea level rises and the shoreline advances inland Regressive Sequence 0 Sea level falls shoreline retreats seaward Sedimentary Resources 0 1 BTU British Thermal Unit 1055 Joules is the heat you need for 1b of Water 1F Sources of Enerqy Nonmetallic Resources 0 Stone Clays Salt Phosphate Rock Cement Sand and Gravel other nonmetals Metallic Resources 0 Iron aluminum copper lead zinc manganese other metals Enerqy Resources 0 Petroleum coal natural gas Buildinq Materials 0 Natural aggregate crushed stone sand and gravel o Gypsum plaster and wallboard 0 Clay tile bricks and cement Industrial Materials 0 Fertilizers Nitrate phosphate and potassium compounds are important to agriculture o Sulfur Used to produce sulfuric acid 0 Salt Used to soften water keep streets icefree and as a nutrient Sedimentary Resources Energy 0 COAL o Formed mostly from plant material 0 Along with oil and natural gas coal is commonly called a fossil fuel 0 The major fuel used in power plants to generate electricity 0 Potential environmental problems from mining and air poHqun o The longer in the ground the better the quality OIL AND NATURAL GAS o Derived from the remains of marine plants and animals 0 Both are composed of various hydrocarbon compounds and found in similar environments 0 Oil Trap geologic environment that allows significant amounts of oil and gas to accumulate Basic Conditions for and Oil Trap n Porous permeable reservoir rock n Impermeable cap rock such as shale n Cap rock keeps the mobile oil and gas from escaping at the surface Carbon Cycle Carbon dioxide C02 is one of the most activate parts of the carbon cycle Stored in the plants and then changes into sedimentary rocks CARBON CYCLE Carbon dioxide C02 is one of the most active parts of die carbon Weathering Vaocfzgc Weathering of carbonate F of granite Photosynthesvs 390 3quot Burning and by vegetation Respiration decay oi biomass by and organisms Burning of fossil fuels Burial of V biomass Photosynthesis and respiration of marine d organisms Sediment and sedimentary rock CO entering the atmOSphere 0 leavung the C atmosphere Chapter 8 Metamorphism and Metamorphic Rocks 10615 1011 PM Rock Cycle The Rock Cycle Weathering Transportation Q 1 Deposltion my I Uplift and Exposure gneous rocks Sediments extrusive Lithification Sedimentary rocks Igneous rocks intrusive Metamorphic rocks Metamorphism to change formquot The transition of one rock into another by temperatures or pressures unlike those in which it formed Changes in mineralogy and sometimes chemical composition 0 Every metamorphic rock has a parent rock the rock from which it formed Parent rocks can be igneous sedimentary or other metamorphic rocks During metamorphism the rock must remain essentially solid Metamorphic grade is the degree to which the parent rock changes during metamorphism Progresses from low grade low temperatures and pressures Pam net quotMic rock Shale Slate Iorphism 9 Lewgrade rv Ma mnrphlsm es metamorphism 9 cm le v39uxmllmu and Wmum mge into a form of ligl il ly packed UIIUIIL and in ux 39 quot3 tidy quotMUdlb quotl 3 gm rue PatIn lock Wit tuck Bunodiotiu Folded poi marquot Hammad ffltquot1 lllf39lllll Si39nng Flt39nrwecmnnal innm OHM lcvlnp39tdhmu and promirqu 4 39 Raindran D 39f 1 nrlcnlm Lfy lffh ill mineral Wain wywmml gm r Metamorphism as a Process Driven by 0 Heat 0 Confining pressure 0 Differential stress 0 Compressional stress 0 Chemically active fluids 0 Parent rock HEAT 0 Most important agent Recrystallization the process of forming new stable minerals larger than the original 0 Two sources of heat Geothermal gradient an increase in temperature with depth about 25C per kilometer Contact metamorphism rising mantle plumes CONFINING PRESSURE Forces are applied equally in all directions 0 Similar to water pressure 0 Causes the spaces between mineral grains to close 0 Example a balloon under pressure will pop DIFFERENTIAL STRESS Forces are unequal in different directions 0 Stresses are greater in one direction COMPRESSIONAL STRESS Rocks are squeezed as if in a vice Shortened in one direction and elongated in the other direction CHEMICALLY ACTIVE FLUIDS Enhances migration of ions 0 Aids in recrystallization of existing materials 0 In some environments fluids can transport mineral matter over considerable distances PARENT ROCK 0 Most metamorphic rocks have the same overall chemical composition as the original parent rock 0 Mineral makeup determines the degree to which each metamorphic agent will cause change Metamorphic Textures Foliated 0 Texture describes the size shape and arrangement of mineral grains Fr A Before metamorphism Unilatm stress p O as v C 3 8 After mumomhum DanIial stnss tion of lit parallel to structural pebbles D bs pendicular to Original neatly spherical wan grains Llippao along crystal talcum callus grains olonpu porpondicular direction oi math m and total cl Foliated Textures um 9quotquot 0 Rock or slaty cleavage Rocks split into thin slabs Develops in beds of shale with lowgrade metamorphism o Schistosity Texture Platy minerals are discernible with the unaided eye a Mica and chlorite flakes begin to recrystallize into large muscovite and biotite crystals Exhibit a planar or layered structure Rocks having this texture are referred to as schist o Gneissic Texture During highgrade metamorphism ion migration results in the segregation of minerals into light and dark bands Metamorphic rocks with this texture are called gneiss Although foliated gneiss do not usually split as easily as slates and schists o Other metamorphic textures Nonfoliated metamorphic rocks are composed of minerals that exhibit equidimensional crystals and lack foliation n Develop in environments in which deformations is minimal Porphyroblastic textures n Unusually large grains called porphyroblasts are surrounded by a fine grained matrix of other minerals Common Metamorphic Rocks Metamorphic Rock Phyllite Foliated Comments Parent Rock Composed of tiny chlorite and mica akes breaks in flat slabs called slaty cleavage smooth dull surfaces Medium to coarsegrained scaly loliation micas dominate Rocks m 0 Very finegrained 0 Excellent rock cleavage Coarse grained compositional banding due to segregation of light and dark colored minerals Medium to coarsegrained relatively salt 3 on the Mohs scale interlocking calcite or dolomite grains Medium to coarsegrained very hard massNe fused quartz grains Very negrained often exceedingly tough and durable usually dark colored 0 Most often generated from lowgrade metamorphism of shale mudstone or siltstone o Phyllite 0 Degree of metamorphism between slate and schist o Platy minerals are larger than slate but not large enough to see with the unaided eye 0 Glossy sheen and wavy surfaces 0 Exhibits rock cleavage Schist 0 Medium to coarsegrained 0 Parent rock is shale that has undergone medium to high grade metamorphism o The term schist describes the texture o Platy minerals mainly micas predominate 0 Can also contain porphyroblasts Gneiss 0 Medium to coarse grained metamorphic rock with a banded appearance 0 The result of high grade metamorphism o Composed of lightcolored feldsparrich layers with bands of dark ferromagnesian minerals Nonfoliated Rocks 0 Marble Crystalline rock from limestone or dolostone parent rock Main mineral is calcite Calcite is relatively soft Used as a decorative and monument stone 0 Impurities in the parent rocks provide a variety of colors 0 Quartzite o Formed from a parent rock of quartzrich sandstone o Quartz grains are fused together 0 Pure quartzite is white Iron oxide may produce reddish or pink stains Dark minerals may produce green or gray stains Hornfels 0 Parent rock is shale or clayrich rocks OOOO 0 Baked by an intruding magma body Metamorphic Environments 0 Contact or Thermal Metamorphism 0 Results from a rise in temperature when magma invades a hostrock o Occurs in the upper crust low pressure high temperature 0 The zone of alteration aureole forms in the rock surrounding the magma Hydrothermal Metamorphism 0 Chemical alteration caused by hot ironrich fluids circulating through pore spaces and rock fractures 0 Typically occurs along the axes of midocean ridges Black smokers are the result of the fluids gushing from the seafloor Burial Metamorphism 0 Associated with very thick sedimentary strata in a subsiding basin 0 Gulf of Mexico is an example 0 Subduction Zone Metamorphism 0 Sediments and oceanic crust are subducted fast enough that pressure increases before temperature 0 Regional Metamorphism o Produces the greatest quantity of metamorphic rock 0 Associated with mountain building and the collision of continental blocks Metamorphism Along Fault Zones 0 Occurs at depth and high temperatures 0 Preexisting minerals deform by ductile flow Mylonites form in these regions of ductile deformation 0 Impact Metamorphism o Occurs when meteorites strike Earth s surface Product of these impacts are fused fragmented rock plus glassrich ejecta that resemble volcanic bombs called impactiles Metamorphic Zones Textural Variations I39Miia mmg hiic 1 26an Lani I n eimnerais Parent low Grade Intermediate Grade High Grade metamorphism to regions of highgrade metamorphism Chapter 11 Deformation amp Mountain Building 10615 1011 PM Rock Deformation a general term that refers to all changes in the shape or position of a rock body in response to stress Causes and Definitions 0 A Undetermed rock B Compressional stress Structures and features that result from forces generated by the interactions of tectonic plates Stress the force that deforms rocks Stresses acting on a rock gt it s strength deformation by flowing folding fractures or faulting Confining pressure and differential stress Types of Stress Compressional stress tensional stress and shear stress C Tensional stress stretching D Shear stress sliding and tearing shortening Strain Change in rock shape caused by differential stress By sliding the top at the deck relative to the bottom we can illustrate the type of shearing that commonly occurs along closely spaced planes of weakness in rocks Shear stress causes the circle in this deck of cards to become an ellipse which can be used Kto measure the amount and type of strain Elastic Deformation The rock returns to nearly it s original size and shape when the stress is removed Once the elastic limit strength of a rock is surpassed it either bends ductile deformation or breaks brittle deformation 0 Example bouncy ball Factors that affect rock strength 0 Temperature Higher temperature rocks deform by spongy deformation whereas cooler rocks deform by brittle deformation 0 Confining Pressure confining pressure squeezes rocks making them stronger and harder to break 0 Rock Type Crystallize igneous rocks generally experience brittle deformation whereas sedimentary and metamorphic rocks with zones of weakness generally experience limp deformation 0 m Forces applied over a long period of time generally result in limp deformation Rock Structures Formed by Ductile Deformation FOLDS During crustal deformation rocks are often bent into a series of wavelike undulations called folds Characteristics of Folds 0 Most folds result from compressional stresses that result in a shortening and thickening of the crust ANTICLINE AND SYNCLINES Anticlines are upfolded or arched sedimentary layers 0 Oldest stratva are in the center Synclines are downfolded or troughs of rock layers 0 Youngest strata are in the center A m Syllmical ION Asymmetrical Mi 0Vth Md Axial plane Axial Diane Anal plane Asymmetrical told quotmm W DOMES AND BASINS Domes are upward circular features 0 Oldest rocks are in the center Basins are down warped circular features 0 Youngest rocks are in the center Youngest strata 39 Oldest strata A Upwarping produces a dome B Downwarping produces a basin MONOCLINES Large steplike folds in otherwise horizontal sedimentary strata As blocks of basements rocks are displayed upward the ductile sedimentary strata drape over them M o I o c I Eat Kailnb Monocllue Arizona I Rock Structures Formed by Brittle Deformation FAULTS Faults are fractures in rocks along which displacement has occurred Sudden movements along faults are the cause of most earthquakes Normal Faults TENSIONAI STRESS u I 3 V After erosion COMPRESSIONAI STRESS f A a quot 4 5 l t 39l l l quot I Q w 9 vm v n a L W ampgtV a k Q quot l J l 9 V 39 I 1 y 9 i quotVV quot A A if hoaxes COMPRESSIONAI STRESS JOINTS Joints are fractures in a rock where there has been no rock movement Moist joins appear in parallel groups Mountain Building Collisional Mountain Belts L Pm I lie colllslon d India and Ash bdla39s nudism nugln consisted nl a thick mm at codanal lal sud sodium nevus Asia s was an m continual llama m a ll developed acetone y um and volcanic art I The cullml cellular loldod and fall In canal met on lay along the annals ol mm cominnnu a loan the Khulna this mnl was lulu0d by In padual awn ol m Tllutan Hm as lie maniacal 0 India was shared undo Am CordilleranType Mountain Belts lnaclivo mammalst a at Tteocl Accm lon of 39 4 quot l V Island ll 2 A r Q to comment 2quot 39 0050 9 A A mchl and a volcanlc island an am being cam I no volcanic island at is sliced all the sundown plan and lwud a suction m ma onlo Ibo comm Nielcontinual uequot 39 ACCfEth ol mucloconlmom 7 D the acctdon cl lb ammolineal lo m munm c A m sudelm ton lam mad ol no old Mullen auxin shoves lie mm island an funnel inland and grows zone on un nml mmin amid a AndeanType Mountain Belts Acmlionry mm volcanic at Suhduclonn 01 plate and lotmalmn ol accustuonmy wedge 8 Plan emuco man 1 Mon um and natal inciting produces a continental volcanic ate Concussion locus and igneous swim um Mom and mm In an dentin In Win Inn fr Bathol r39 39439 c Uplmed l quotccvet quot339y Uplulhng and evosnon e 38 exposes batholltll consming of numerous plulnm c SWMII at and is lulud by a period a unlit Isotasy Less dense crust float on top of the denser rocks of the mantle The concept of floating crust in gravitational balance Envision a series of differentsized floating blocks on water
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