Midterm/Exam 2 Study Guide
Midterm/Exam 2 Study Guide Geol 121
Popular in Physical Geology 121
Popular in Education and Teacher Studies
This 10 page Study Guide was uploaded by Summer Jones on Saturday October 17, 2015. The Study Guide belongs to Geol 121 at Towson University taught by Gregory Shofner in Summer 2015. Since its upload, it has received 124 views. For similar materials see Physical Geology 121 in Education and Teacher Studies at Towson University.
Reviews for Midterm/Exam 2 Study Guide
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 10/17/15
GEOLlZl Exam 2 Study Guide FA15 Shofner Content roughly equal coverage from each of the following areas 1 Sedimentary Rocks and the processes that form them 2 Metamorphic Rocks and the processes that form them 3 Streams Sediments Sediment types Clastic pieces of broken rock and minerals moved as solid particles Chemical dissolved ions in and water transported in water Biochemical sediments with a biological origin result of biological activity or actual biological material Sediment sources Clastic primary source is igneous or metamorphic rocks but can also be other sedimentary rocks or sediment deposits remobilized sediments Chemical chemical weathering of rocks Biochemical decay of biological material plants or hard parts of organisms Weathering physical and chemical the inplace breakdown of rocks Erosion movement of weathered material away from the location of weathering Classification of Clastic Sediments and Sedimentary Rocks Size diameter of grains Gravel is gt 2mm Sand is 006 2 m can be seen with the unaided eye Silt is 0004 006 mm cannot be seen with the unaided eye Clay is lt 0004 mm cannot be seen with high magnification Shape degree of roundness angular to rounded Sorting distribution or range of grain sizes wellsorted to poorlysorted Composition a secondary classification mineral or rock fragment type Angular 1blewmeattruly Pearly Moderately Weill Very well serted sorted serted sorted sorted Sediment Transport Gravity Wind Ice Fluid mainly water Increasingly Larger particles requires increasingly Higher hydraulic energy for transport Changes in properties with distance from sediment source Size decreases typically more rounded and better sorted Composition also indicates distance and time quartz is high resistant to physical and chemical breakdown and persists for long time feldspars and mafics weather quickly and therefore do not travel far or for long times Sediment Maturity In the broadest terms distance from source is indicated by 1 Coarser to ner sized grains 2 Poorly to well sorted grain distribution 3 Angular to rounded grains and 4 increasing Quartz abundance Increasing distance of sediment transport over longer periods of time promotes more extensive physical and chemical alteration Alluvial fan More mature Transportation and Deposition Clasts are deposited when the transportation energy is insufficient to move the particle As transportation energy decreases the larger heavier particles are deposited first HIGH ENERGY environments can transport large and small particles LOW ENERGY environments can transport only small particles Low Energy Environment High Energy Environment Lagoon Streams Deep Lake River deltas Deep Ocean Mountain valleys Coastal mud ats Wetlands Sedimentary Structures Bedding Planar bedding mostly uniform in thickness over large distances Cross bedding parallel sloping surfaces usually occurs in sets Dunes in rivers or deltas and in deserts Graded bedding coarse to finer particles from bottom to top Submarine gravity ows also fans on land Ripple marks like crossbeds but smaller Crossbeds and ripple marks tell us about transport direction crossbeds slope toward direction of transport asymmetric ripples also have their steep slope in direction of transport symmetric ripples are bidirectional Sedimentary Rocks Clastic rocks classified just like sediments Size Shape and Sorting Composition generally a Secondary Classification Conglomerate poorlysorted coarse grained most grains gt 2mm sub to wellrounded Breccia poorlysorted coarse grained most grains gt 2mm usually very angular Sandstone moderately to wellsorted finer grained sand sized commonly tends toward rounded but doesn t have to be Siltstone moderately to wellsorted fine grained silt sized commonly tends toward rounded but doesn t have to be Shale or mudstone typically wellsorted but can t see this very fine grained microscopic clays don t become rounded siltstone shale breccia Biochemical Biological material decayed plant materials gradually lose all but the carbon from the plants producing these materials in succession peat 9 lignite 9 coal changes induced by heat from burial Shells hard parts of organisms fall to bottom of marine basin and become lithified hardparts of corals and other reefbuilding organisms are preserved in place These are mostly composed of calcite a carbonate mineral Silicabased rocks silicacomposition organism hard parts primary example is Chert Carbonates Limestones Classified based on type of clasts and the amount of carbonate mud higher mud content represents lower energy environment lower mud content represents higher energy environment Mostly negrained low energy 1 Mostly coarseegrained high energy Sedimentary Facies bodies of rock with distinct physical properties that represent a particular depositional environment tells us what the geological conditions were tectonics global climate glaciations where the sediments came from and changes in sediment supply and rate of deposition Sandstone at or near shore river and delta deposits Shale further out in basin past delta Carbonate deeper water Changes in stacking patterns indicate changes in sea level ie shifting of depositional environment due to water depth fining upward sequence 2 sealevel rise coarsening upward sequence 2 sealevel fall Significance is that sealevel changes are tied to regional tectonics uplift and subsidence continental breakup or assembly longterm tectonics continental glaciations global climate shifts top of rock sequence E transgression marme mild Transgression sea level rise a 7 a r Deepening upward sequence regression Rock type changes from I g shoreline to marine facies falling sea level bottom of rock sequence Vertical stacking of rocks at fixed basin locations top of rock sequence Regression sea level fall Shallowng upward sequence Rock type changes from carbonate marine to shoreline facies marine mud bottom of rock sequence Metamorphism and Metamorphic Rocks Changes to preeXisting rock protolith due to some combination of elevated Pressure elevated Temperature and the presence of Chemically Reactive Fluid mainly water Changes in texture and mineralogy Overall chemistry typically remains the same but commonly the mineral assemblage is entirely different than the protolith same composition different texture same bulk composition different mineral assemblage quartz clay and intergrewn and iron amide interlocking grains Fossil mum h mf5 metamorphic rock limestone prololilh sheila protolith quartz feldspar bietite and garnet metamorphic rock eVlo nw 0 same composition increased grain size f 001 he limesto spar crystals mmmwu marble The characteristic feature in metamorphic rocks is an oriented or foliated texture Formed in respo nse to differential stress stress very strong in a single direction Texture grain size gtgtgt coarseness of foliation Composition mineral assemblage increasing crystal size W aghi 739 39 if 3 increasing coarseness of foliatian hm3Ill s Nonfoliated metamorphic rocks form from minerals that have not preferred orientation equant and not elongate or platy grains Characterized by granular texture of interlocking grains with little or no foliation Typically formed as contact high T only metamorphism or subduction zone metamorphism limestone protolith sandstone prototi th mafia protolith t s hornfels r1i39nt Increasing metamorphic grad E gt blueschist typically has a foliated texture devtton quot i ous39quot quot 39 hyd f fb an but 1s 1nciuded here because of itsunlque zone contact alteration of compos1t10n and 1nt1mate assoc1at10n w1th ultramafic rook subduction zones Metamorphic Grade Describes the Intensity of Metamorphic conditions P and T not found 7 E in nature Conditions 7 Temperature 35 am 300 son sou mm 300 9010 1000 39 39 V1 F I 0 f 10 U wetgmnlte Ifgstarlzsto melts I 3 I 7 WI 2 0 w x g I wetbasalt I 7 7 a l 39 quotistartetomelt 9 iiiquot an a Index Minerals used for mapping regional metamorphism ie describing the distribution of metamorphic rocks over a geographic area typically in regions of mountain building Index Minerals are stable over some set of P amp T conditions and represent differing degrees of metamorphic intensity Regions with rocks containing the same index minerals form metamorphic zones NOTE lower grade index minerals can coexist with higher grade index minerals but the metamorphic zone is defined based on the presence of the highest grade index mineral mgammamatms and Ilnrrdteitgmji igte als I Parent L Grade Immediate made High ra ei Ell i 1 l A g ay Hm I i lsrh lgtamrphui d L 39 hhnit e mne Hi iEii iill l E 2m ism EraEH Ishmael3mm quot K 39 I Highgrade i Eril imn te mne Metamorphic Facies Associated with a particular set of P T conditions that represent distinct geologic settings most commonly different tectonic regions or boundaries BUT the mineral assemblage for a particular rock is strongly in uenced by the protolith composition a nd not the geologic setting e g basalt VS shale Ditagenesis Temperature 30 o f 0 if 40 00 M 39 I Homfe s Facies f g Greenschlst 10 4 y A W quot Amphiboliite quot quot 39 I Facies 6 7 ms r G ranuutte 20 m Pressure ikillobars l Q Depth kilometers Not 12 39 fou ud 3940 I im nature 14 EC log te Fables 50 Streams see supplemental slides Know what drainage basins and drainage divides are Know that drainage network type re ects the underlying geology ie presence of geologic structures types of sediments e g on glacial till Know what the three states of a stream system incision aka downcutting active erosion of the stream channel stable dynamic equilibrium aggradation active sediment deposition building dunes bars etc mostly controlled by base level Know what base level is elevation below which a stream channel can no longer downcut its channel can be local base level like a lake or waterfall ultimate base level is the ocean surface level Changes in base level result in two basic types stream features incised meanders meanders are usually atlying and not within a canyon terraces different levels of oodplains shown by steps in the land surface Know that base flow in streams is the water from groundwater so ties into groundwater ow gaining or perennial stream when groundwater ows into stream losing or emphemeral stream when groundwater level below stream channel and stream ows downward into underlying rocks or sediments and maybe into groundwater Know about discharge should be able to recognize the equation and infer things from it ie effects of velocity and crosssectional area on discharge Know that channel roughness affects discharge because of increased friction Know about velocity distribution in channels ie Vshaped downstream laterally and vertically both due to friction with stream channel banks and base respectively Know that highest velocity in meandering stream is closer to the cut banks on the outsides of meander bends than to bars on insides of meandering bends Know about sediments transported by a stream total load includes clastic material and dissolved chemical elements capacity maximum quantity of sediment that a stream can carry competence maximum particle size a stream can carry Be able to look at the Hjulstrom diagram shows particle size and velocity and interpret size and velocity relationships to erosion transportation and deposition Know about stream gradient ie mainly what it is and how it changes from upstream to downstream related to this is the change in stream channel shape and crosssectional area from upstream to downstream ie Vshaped straighter channel to broad ushaped meandering respectively know about changes in discharge velocity crosssectional area total sediment load and maximum grain size from upstream to downstream Know about meandering streams where they erode and deposit and that their channels migrate and change shape over short periods of time Know relationship between uplift and erosion and direction of stream ow including that direction can change with landscape changes
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'