Final Exam Study Guide
Final Exam Study Guide GSC 110D
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This 22 page Study Guide was uploaded by Amanda Hillegass on Sunday April 26, 2015. The Study Guide belongs to GSC 110D at University of Miami taught by Terri Hood in Spring2015. Since its upload, it has received 266 views. For similar materials see The Earth System (lecture) in Geology at University of Miami.
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Date Created: 04/26/15
GSC 110 Dr Terri Hood Exam Date 542015 Study Guide for Exam 3 1 Earthquakes a b c d e What is an Earthquake i Motion produced when stress within the earth builds up over time until it exceeds the strength of the rock rock fails by breaking along a fault Fault i Fracture in Earth s crust where slipsliding occurs on side relative to the other ii Some are vertical extend below surface but most sop at an angle fault plane iii Movement on many faults happens in a discrete event force trying to move both sides overcomes frictional resistance quotstickslip behavior Earthquake geography i Focus hypocenter center of energy release during earthquake point where initial rupture occurs ii Epicenter point directly above focus on surface usually has the most ground motion iii They occur due to sudden movement on a fault iv Makes sudden pushpull on rock l sends out shock from focus seismic waves v Seismic waves trave very quickly 10002000x speed of sound vi 3 types 1Pwaves primary waves fastest 2SWaves secondary waves 3Surface waves trave only along ground surface not through earth Measuring Earthquakes i Seismograph instrument that measures ground motion from an earthquake ii Use three 1 for vertical motion 2 for horizontal at right angles Locating an Earthquake Epicenter i Use arrival times of seismic waves ii Unless at epicenter order of arrival is Pwaves Swaves Surface waves then aftershocks iii Time lag between their arrival increases as you get farther from the epicenter iv Time delay of Pwave and Swave arrival can be used to calculate distance from epicenter v Using this distance at three different locations triangulate to locate epicenter f Earthquakes How big i Mercalli Intensity Scale 1Defines intensity by amount ofdamage it causes 2Scale of 1 12 in roman numerals al smallest felt by humans bV wakes people things fall over cX many buildings completely destroyed 3Useful in reconstruction of historical earthquakes ii Richter Magnitude Scale 1Based on largest amount of ground motion factors in distance from epicenter 2Logarithm of amplitude a10mm 101 M 1 etc bM lt 2 isn t felt c M6 moderate damage dM89 absolute damage 3There are more smaller magnitude earthquakes than large ones 2 Earthquake Damage a 73pes of Earthquake Damage i Damage due to ground motion 1Source of ground motion most earthquake motion is caused by surface waves aRayeigh Waves pass by like ocean waves updown motion bLove Waves pass by like snake lateral side to side motion c Damage depends on i How close you are to epicenter ii Nature of substrate underlying ground l least damage solid bedrock most damage loose sediments iii Building construction d Building to minimize earthquake damage i quotBase lsolatorsquot Te Papa museum Wellington New Zealand shock absorbers ii Makes whole building move as one lead rubber ii Landslides and Avalanches 1Ground on steep slope gives way tumbles downhill California coast iiiSediment Liquefaction 1Shaking of sediment containing pore water water trapped between sediment grains l unstable quotslurryquot like quicksand 2Can create sand volcanoes sand erupts through overlying layers ivFires 1Fires spread from stoves lamps broken gas lines v Tsunamis 1Japanese for harbor wave commonly called quottidal wavesquot have nothing to do with tides 2De nition giant wave caused by submarine fault submarine landslide submarine volcanic eruption and bolide impacts in ocean aka asteroidcomet 35udden vertical displacement of sea oor generates wave in overlying water 4Height of tsunami depends on earthquake magnitude and volume of sea oor displaced 5ln deep water aWave height is very small less than 12 m but is moving whole body of ocean bWaves travel very fastup to 800 kmhr cTsunami carries a tremendous amount of energy 6As wave approaches shore a Friction with sea oor causes wave to slow and pile up bNorma tsunamis reach heights up to 10 m 30 ft 7Landslide and impact generated megatsunami can get 1020X biggerl Asian Tsunami Dec 2004 8Dealing With Tsunamis a Tsunami Prediction i Seismographs record initiating earthquake give epicenter location and magnitude ii Oceanwide array of instruments detect passing tsunami whole oceanbody motion gives speed iii Tsunami warning issued iv Problem can t accurately predict runup maximum vertical height onshore above sea level without knowing amount sea oor was displaced bMinimizing Tsunami damage i Identify tsunami runup areas ii Evacuation plan iii Avoid new development in highrisk areas iv Design new construction to minimize damage 3 Earthquake Prediction and Location a Where do Earthquakes Happen i Plate boundaries ii Divergent Boundaries 1Shallow focus lt70 km deep because partially molten mantle is rising toward surface 2Less intensedangerous than EQs at other 2 boundaries iii Transform Boundaries 1Shallow to deep focus up to 650 km below due to mantle s plastic nature 2Minor to major EQs 3Ex North Anatolian Fault Turkey San Andreas Fault 4Motion is often distributed in a complicated way along a series of faults 5Stress of plate movement spreads out farther where sections of main fault are quotlockedquot iv Convergent Boundaries 1Mostly subduction zones shallow to deep focus lt650 km and minor to major 2 Most destructive EOs occur along upper surface of subducting plate as it s forced beneath overriding plate BenioffWadati Zone 3Subducting at shallow angle l Benioff zone EQs spread out lateraly 4Subducting at steep plunge angle l narrow zone of intense EQ activity b What about earthquakes that happen far away from plate boundades i lntraplate Earthquakes intra inside C Sources of lntraplate Earthquakes i Collision Zones 1Convergent plate boundary where 2 continental plates collide neither descends 2Ex lndian Asian plates collision Himalayas create severe fault zones extending into Northern China ii AncientInactive fracture zones that remain weak 1 Many are failed rift valleys aPresent day locations of some major rivers ex Amazon Niger Mississippi Rivers 2New Madrid Seismic Zone aLies above ancient failed rift valley b18111812 New Madrid EQ 5 quakes gt M8 changed course of Miss River large sand volcanoes severe aftershocks 3St Lawrence River iii Extensions of midocean ridge fracture zones 1Transform faults between segments of spreading ridges remain structurally weak once formed 2Fracture zone extension 3Positive big Intraplate EQ s are less frequent than plate boundary EQs 4Negative When they occur effects extend much farther from epicenter d Earthquake Prediction i Longer Term id seismic zones geographic clusters of historic epicenters 1Areas of high risk seismic gaps sections of active fault that haven t moved for many years pressure building ii Shorter Term foreshocks cluster of small EQs immediately preceding a large one 1Hard to tell difference between this and small EQ not useful e Induced Earthquakes i EQs caused by human activities happen in areas experiencing geological stress ii Due to 1 Changing quotStress eld of the area 2ncreasing pore pressure of waterubricate locked faults iii Situations where they occur 1Reservoirs up to M 65 loading higher water pressure aLines of evidence epicenters located under reservoir timing of EQs with high water levels 2 Withdrawal of oil or water aChanges stress eld due to subsidence 3Deep well injection aPump uids deep into ground for oil recovery or waste disposal radioactive material spent fracking uid wastewater 4Rockbursts up to M 4 aDue to mining activity sudden implosion of tunnel walls responsible for 50 of mining fatalities 5 Underground Nuclear Testing aVs atmosphericunderwater testing trying to contain radiation blnitial detonations up to M 6 concern of aftershocks and creation of new faults 4 Crustal Deformation a Crustal Deformation Faulting and Folding i Regional geologic forces produce differential stresses that produce deformation These are 1Compression squeezing tension stretching and shear twisting b Deformation i Small scale foliation joints c 039 e f 9 ii Large scale folds bentwrinkled layers faults fractures on where one rock body slides past another iii Kinds of Deformation 1Brittle material breaks into pieces ex faults 2Ductile material changes shape Without breaking ex folds iv Behavior depends on deformation rate quicker more brittle composition temperature higher more ductile con ning pressure higher more ductile Faults i Most aren t completely verticalhorizontal ii Terms for 2 sides come from mining 1Hanging wall side above fault plane hanging above you 2Foot wall side belowfault plane below your feet Describing Orientation of a Fault i Same as describing any planar surface ii Strike angle between horizontal line on plane and true North gives geographic direction iii Dip angle between horizontal and steepest slope on plane perpendicular to strike gives slope 73pes of relative movement on a Fault i Dipslip faults sliding up or down along dip direction ii Strikeslip faults one block slides horizontaly past the other along strike direction iii Obliqueslip faults have components of both vertical lateral motion Dipslip Faults i Normal Faults hanging wall moves down foot wall 1Due to pulling blocks apart extension crustal lengthening ex Basin and Range province ii Hanging wall moves up foot wall 1Due to compression crustal shortening ex Himalayas 2Reverse fault if a steep dip gt 35degrees thrust fault if shallow dip lt 35 degrees iiiStrikeslip faults 1Regional shearforces associated with transform boundaries ex San Andreas Fault 2De ned by relative motion of opposite side leftright lateral Folds i Most caused by compressional forces l crustal shortening ii Center bows up anticline bows down syncline iii Interesting time sequences exposed due to erosion back to horizontal 1Anticline oldest layers in center 25yncine youngest layers in center iv If hinge of fold greatest curvature isn t horizontal plunging antisyncline v Dome fold shaped like upside down bowl center oldest vi Basin fold shaped like right side up bowl center youngest h lsostacy Greek quotequal standingquot i Describes buoyancy of lithospheric plates ii Archimedes Principle 1Blocks sink until mass of water displaced entire mass of block ex icebergs 2Areas meeting this criteria are in isostatic equilibrium 3Rues of lsostacy a Thickerlithospheric plates rise higherthan thinner l mountains have roots bLess dense lithosphere rises higher than more dense avg density continental 27 oceanic 29 i Oceanic thin dense l lower ii Continental thick less dense l higher 4L0ading lithosphere causes it to sinkice sheets high sedimentation rate 5 Unloading causes it to rise aAreas still moving updown are undergoing isostatic adjustmentcompensation Ex quotreboundquot of Canada N US from removal of ice sheets 5 Fossil Fuels and Coal a Resources of minerals and energy i Energy resources geological l geothermal energy nuclear energy l fossil fuels b Fossil Fuels i Altered remains of previously living plants and animals ii Essentially stored solar energy that reached earth long ago iii Geological processes have concentrated and re ned combustible material more energy per amount burned l coal oil natural gas c Coal i Formed from plant material mostly in swampy forests ii Steps 10rganic matter is buried in oxygenpoor environment does not react with 02 to form C02 2Compaction and partial decay transform it to peatgt 50 C 3Deep burial 410 km drives off other components except carbon gt coal iii Grades of Coal Low grade gt high grade d e f 9 Lignite l Anthracite 70 C 95C Coal Exploration i Sedimentary bed of coal coal seam ii To nd coal seams search for ancient strata deposited in warm swampy environments iii US has abundant coal deposits from Paleozoic and Mesozoic Eras Methods of Coal Mining i Strip Mining 1For shallow seams lt 100m deep overburden is scraped off the coal removed 2lf area is then left in this state lack oftopsoi prevents revegetation 3quotClean coalquot scrubbing it of certain chemicals 4ncreased environmental awareness l reclamation top soil replaced revegetation proceeds ii Underground Mining 1Tunnels dug to mine deeper seams usually anthracite 2Hazards tunnel collapse explosion methane gas and black lung disease inhalation of coal dust iii Both methods of coal mining can lead to underground res 1Once lit coal deposit res are very dif cult to put out 2Some have burned for decades entire communities abandoned Centralia PA burning last 45 years Oil and Gas i Oil petroleum and natural gas currently supply more than half of the world s total energy use ii Natural gas oil and tar are all hydrocarbons Oil and Gas Formations i Microscopic plankton algae animals in body of water lakeocean die settle to oxygenpoorenvironment organic rich clay accumulates ii Lithi cation black organic shale iii Burial increased TP l kerogen waxy organic molecules oil shale 1Can be minedprocessed to quotsyncrudequot and then to plastics and other petroleum products iv Further increases in T P gt 4km depth l cracking of kerogen 80C oil 160C gas v Rock formation in which all of these processes occur is the source rock vi Processing of oil contained in source rock is labor intensiveexpensive Bituminousl 85 C vii Once oil and gas form they tend to migrate upward viiiCan escape to surface ex La Brea tar pits ix Can migrate into reservoir rocks oil is accessible and easily extracted h Oil Reservoir Rock need i High porosity pore space ii High permeability connectivity between pores iii Trapping mechanism stop oil from owing up past reservoir i Oil traps need i Seal rock impermeable overlying rock that prevents oil and gas from moving further upwards ii Oil trap geometry 3D geological situation that focuses oilgas migration into trap j Environmental Considerations i Negative impacts of oil drilling and transportation 1Ecological footprint of drilling operations 2Oil spills from drilling operationtransport aDeepwater Horizon Oil Spill i April 2010 to JulyAugust 2010 ii Largest offshore oil spill in US history iii Deep water 1 mile depth oil well in N Gulf of Mexico k Peak Oil i Theory 1For any geographic region rate of petroleum production over time follows a bellshaped curve 2Early goes up discoveries infrastructure addition 3Late foes down resource depletion 43 factors determine specifics of a curve aDiscovery rate production rates total production area under curve ii M King Hubbert s U5 prediction 1Geophysicist predicted in mid 1950 s that Us oil production would peak around 1970 2People laughed at theory but he was right iii World Oil Reserves 140 of 54 oilproducing countries are past peak production 2Other 14 predicted to peak before 2020 iv quotSecond Half of Oilquot 1Remaining reserves are tougher to get at more accidents per amount of oil produced and takes more energy to obtain 2 EROI aEnergy Return on Energy Invested bBefore reserves run out they take more energy to obtain than they provide last 14 of bell curve l useless 3Demand for energy is still increasing 4Will be felt most in industries requiring liquid fuel like air travel 50ther farreaching effects 6 Methane Hydrate and Fracking a Other Sources ofNatura Gas Not associated with oil deposits i Methane Hydrate ii Hydraulic Fracturing quotfrackingquot iii Natural gas 95 methane CH4 highly ammable can form methane hydrate in deep ocean sediments gt1600 ft b Methane Hydrate c i Frozen Methane water in large deposits on continental shelves ii Sudden release of methane due to warming causes 1Sinking ships ex Bermuda Triangle 2Rapid warming at end of ice ages methane greenhouse gas 20x stronger than C02 Hydraulic Fracturing fracing fracking i Injection of high pressure solutions water sand chemicals into impermeable gascontaining rocks mostly shale to allow extraction of natural gas ii Most gascontaining formations are deep 8000 ft below surface iii How 1Wel is drilled vertical then horizontal 2Liner quotcasingquot put in place At the level of the water table 3Waterbased solution injected to induce cracking 4Natural gas solution recovered iv Shale gas plays economically signi cant formations v Most oil states have exploited their deposits vs Northeastern US vi Energy from natural gas projected to surpass oil in US by 2030 vii Environmental concerns of Fracking 1Drill pad construction and operation 2Water consumption single injection well uses 4 million gallons of water it can t be reclaimed for human use 3Groundwater Contamination most likely cause improper sealing of well casing where it passes through the groundwater zone aContaminants methane chemical additives bMake up 052 of fracking solution and serve various purposes c Some are toxic and carcinogenic dAmounts a typical injection well site uses 4 million gallons of solution 80300 tons of chemicals 4Dealing with quotFlowbackquot fracking solution that comes out with natural gas aEnvironmentallyideal solution safe temporary storage and reuse in fracking bncreasing amounts of owback are being disposed of underground using deepwell injection c Induced earthquakes have been observed 7 Mass Movement a Landslides and Other Mass Movements i Mass Movement 1Gravity caused transport of material rock soil sediment snowice 2Happens when slop becomes steeper than the critical angle angle of repose ii Angle of Repose steepest slope a pile of sediment can have and remain stable 1ncreases with increasing grain size and increasing grain angularity iii Other factors affecting possibility of Mass Movement 1 Vibration earthquake 2 Presence of Water lubricates increases chancesspeed of movement 3 Vegetation stabilize slopes decreases movement b Major Types of Mass Movement slowest to fastest i Creep 1Gradual downslope movement of sedimentsoil 2Travels a couple cmsyr 3Gravity freezethaw cycles in temperate climates creep ii Slump 1Block of material detaches along a spoon shaped sliding surface glide horizon and slips downslope in semi coherentfashion more rotation of soil iiiMud owDebris Flow 1 Water mixed with sediment moves down a slope 2Fine grained sediment mud ow ex lahar volcanic mud ow 3Larger rocks within sediment debris ow 4Follows River valleys can move up to 100 kmhr ivAvalanche 1Turbuent cloud of debris mixed with airthat rushes down slopes at high velocities 2Snowdebris avalanches 3Trave up to 250 kmhr v Landslide 1Bedrock detached from slope moving quickly downhill on glide horizon paralleling slope surface 8 2Travels up to 300 kmhr faster with air cushion under mass 3lf large landslide hits body of water generates megatsunami aEx Vaiont Dam 1963 Italian Alps bHighest potential for these are on volcanic islands ex Hawaiian islands Lituya Bay in Alaska c La Palma off W coast of Africa shows signs of slope instability l could generate megatsunami that would take 6 hrs to reach Miami and could travel 15 miles inland if entire side of active volcano went viRockfall 1Mass free fall from a steep cliff often happens in Spring bc of frost wedging 2Forms talus sloping pile of rocks along base of a cliff unstable c Methods to Stabilize Slopes i Common along roads 1Retaining wall avalanche shed rock bolts terracing making steps and revegetation wdeeprooted species preventative measure ii Dealing with side effects of water 1 Relocate water ow lower water table dries out glide horizon managed reservoir and ripraps absorb wave energy along coasts d Submarine Mass Movements Type of Movement Submarine slump Submarine debris ow matrix Turbidity Current Sediment dispersed in water i Turbidity currents rst observe in reservoirs largescale fast moving and frequent in ocean margins 1When material settles it forms graded beds quotturbiditesquot ii Areas of frequent submarine mass movement 1Hawaii submarine slumps debris ow 2East Coast U5 debris ow turbidity currents 1929 Grand Banks earthquake generated a turbidity current moving 65 kmhr clocked by timing breaks in transAtlantic cable Coastal Processes a Coastal Processes Effects of windgenerated waves on coastlines i Waves approach shore when water depth shallows to less than half the wavelength wave quotfeels bottomquot slows piles up and breaks ii When they approach shore at an angle part of wave closer to shore slows more than part farther away wave pivots Moving Material Semicoherent blocks Larger clasts mud ending up almost parallel to shore within 5 degrees wave refraction b Effects of Wave Refraction i Wave energy is focused on headlands spread outweakened in bays 1Erodes headlands deposition in bays 2quotStraighteningquot of coastlines over time ii On a straight coastline 1Angular force of waves creates a longshore current transport of sand along shore longshore transportdrift iii Mechanism incoming wave enters at an angle backwash moves straight out with net movement of sand grains being laterally 1Reshapes coastlines so aBuild structures to slowstop longshore transport grains and jetties bResults in deposition on leading side and erosion on down drift side iv Case where beach landforms create current 1Normally wind pushes surface water toward shore water ows back out underneath near bottom undertow 2Some shorelines have a topographic high running parallel to shore ex sand bars or shallow coral reefs 3Prevent return bottom water ow along long sections of the beach aAll return ow focuses at breaks in the barrier rip current causes many drownings blf caught in one swim parallel to the shore c Coral Reefs i Reefbuilding corals found at latitudes 3OS3ON ii Reef forming around volcano on subsiding oceanic plate 1Fringing reef initial reef forming around volcanic island 2Barrier reef wellformed reef encircling lagoon with small island tip of volcano 3Atoll no remnant of volcano above sea level ex Bermuda d Coastlines due to Sea Level Changes Emergent and Submergent Coasts i For last 25 my changes in sea level was dominate by glacial interglacial cycles ii Glacial period sea level drop l emergent coastlines iii lntergacia period sea level rise l submergent coastlines e Submergent Coastlines i Drowned river valleys ex Chesapeake Bay ii Drowned glacial Ushaped valleys fjords iii Special case 1Emergent coastline that form during interglacial period due to isostatic rebound of lithosphere previously depressed by weight of ice 2Crustal uplift outpaces sea level rise 9 Surface Water and Groundwater a Running Surface Water i Formation of streams and drainage networks ii Runoff surface water moving downslope initial sheetwash follows topographic lows or cuts down through weaknesses in the substrate to form streams iii Stream extend upslope by headword erosion iv Smaller streams tributaries ow into larger stream trunk stream v All interconnecting streams make up a drainage network vi The spatial pattern of a drainage network depends on composition of substrate and shape of landscape b Types of Drainage Networks i Dendritic Greek quotDendrosquot tree shaped like branches of a tree streams join in downstream pointing quotVquot form where substrate initial slope are fairly uniform ii Radial radiate out from a central point commonly form around volcanoes or any coneshaped mountain iii Annular Ring forms concentric rings typically overlying domes iv Rectangular follow joints in bedrock ex Canadian Shield glacial areas v Trellis con ned between erosionresistant ridges vi Drainage network collects water from a region watershed vii Ridge or highland that separates watersheds drainage divide viii Continental divide separates drainage basins that ow into different oceans ix Streams merge into rivers eventually ow into an ocean x Nature of River changes as you move downstream down its longitudinal pro le 1Gradient change in elevation of horizontal distance decreases 2 Carrying capacity decreases a Size ofmateriatransported decreases bAmount ofmateriatransported per volume of water decreases c Eventually river goes from dominantly erosional to do min a ntly depositional dDepositional environment oodplain 2 common patterns of rivers i Braided river subdivided into many channels that merge and separate form on oodplains with higher gradients ii Meandering river swing back and forth in snake like curves formation 1 Once river isn t perfectly straight water moves faster on outside of bend slower on inside shift in velocity l erosion along outside of bend deposition along inside 2 Through time loops become more pronounced 3 Once adjacent loops get near enough to each other a new channel cuts between them meander cutoff old loop becomes isolated oxbow lake c River Flooding i Floods occur during seasonsyears of peak discharge ii Flood frequency graphs de ne major interval ood limits 2 10 100yr oods iii ZOOyear ood ex 1993 ooding of Mississippi and Missouri Rivers iv Channelization construction of levees straighten river path protects from minor oods but increases potential of big oods v Water moves faster decreases lag time between heavy rainfall and peak discharge peak discharge is higher once levee is breached water oods adjacent areas more rapidly vi Arroyo canyon that s dry unless there s ooding vii Slot canyons ash ooding creates its own river channel popular sites of hiking viiiSteep gradient gt50 ftmi whitewater rapids waterfalls extreme whitewater 200300 ftmi ix Hydraulics interesting features of water movement turbulent ow caused by interaction of owing water with river sides bottom reason for scouting river sections you are planning to raftkayak x Another factor water volume river at low ow 1000ft3sec same river at higher ow 100000 cfs xi Most dangerous when pushing you againstunder obstacle worst log jams or quotsnagsquot change rating xii Waterfall vertical drop visible from upstream as horizontal line past which you don t see any water 1Deep cavity gouged into riverbed downstream of falls l creates hole aStrong surface backwash pulls boat back into falls mostall of downstream ow is at river bottom bConfiguration of falls determines boat escape direction for hole cA hole Withouta surface escape direction is called a keeper only way out of one is to let it suck you under and pull you along bottom until clear of hole d Groundwater i Water below ground surface held in soil and rocks ii Water storage depends on porosity transmission upon permeability iii Aquifer rock unit that stores and transmits water readily ex Sandstone Limestone iv Aquitard rock unit that does not storetransmit retards oWex shale v Aquiclude stores but doesn t transmit e Aquifers i Uncon ned upper boundary is 1Usually near ground surface 3m separated from surface by an impermeable layer a Easy to access for wells bSurface water source quotrechargequot is locaex rain c Readily contaminated by surface materials ex fertilizers 3Con ned separated from surface by an impermeable con ning layer aCan be signi cantly deeper recharge often far away bLess susceptible to contamination by locasurface activities f Water Table i Boundary between air lled pore spaces above and water lled pore spaces below ii Mirrors topography in a quotdampenedsignal fashion doesn t follow it exactly g Groundwater Flow i Follows hydraulic gradient owing from areas of high potential to areas of lower potential ii Potential is a function of gravity weight of overlying wateroverlying rock h Rate of Groundwater Flow Darcy39s Law i Rate is proportional to hydraulic gradient hydraulic conductivity permeability ease of ow ii Some natural consequences 1Artesian well aWel with free owing water at surface bPenetrates a con ned aquifer in an area of low potential 25prings aGroundwater naturally owsseeps up from below bForm in a variety of ways i Water table intersects ground surface valleys ii Permeable layer or fractured zone intersects ground surface iii Downward percolating water runs into an impermeable layer migrates along top surface to hillside quotweeping wallquot cThere are several historic artesian springs in South Florida 30asis aSpring in a desert region deep con ned aquifer water brought to surface by faultsfolds i Groundwater Usage Issues i Contamination 1Natural Sources aEx iron low pH Fe3 or low 02 Fell Fe2 bEx Hydrogen sul de smells like rotten eggs cArsenic signi cant health hazard iron sulfides concentrate this commonly found in river delta s groundwater 2Human Sources aLeaking underground storage Ex septic land lls fuel storage containers speci cally those under gas stations chemical waste manufacturing plants especially those by rivers and radioactive waste bSurface contamination ex urban oils and grease from roads even tire rubber agriculture and mining acid mine drainage oxidation of pyrite turns water acidic c Point sources create a contaminant plume underground dRemediation cleaning up is dif cult and expensive ex steam injection to drive material into clean up wells ii Groundwater depletion 1Water withdrawal rate exceeds recharge rate 2Causes a number of problems a Local drawdown of water table cone of depression can drain nearby wetlands and cause neighboring wells to go dry bSat water intrusion i In coastal areas fresh water sits as a lense above and adjacent to salt water ii Excessive salt water margin to move inland and upwards l wells go salty c Ground subsidence i Ex Venice coastal areas ii Causes compression of nowdry soil layers dFaiure of quotroofsquot of underground caverns i Stable when lled with water air can t support overburden covercollapse sinkhole 10 Karst Topography a Karst i Slavic quotkarsquot quota bleak waterless placequot features created when groundlsurface water dissolves soluble bedrock usually Limestone most abundant soluble bedrock 1Dissoves in water C02 l H2C02 aka carbonic acid 2Dissoution occurs preferentially along joints fractures and bedding planes b Karst Topography i Surface Karst features cause abnormal drainage patterns deranged drainage ii Features of Karst 1 Caves aNatural underground cavities most common product of limestone dissolution bEstimated that more than half of N American caves haven t been discovered yet 2 Sinkholes aCircuar depressions bSolution Sinkholes i Dissolve from surface down most common c Collapse Sinkholes i Roof over cavern collapse dStreams commonly drain into sinkholes travel through underground caverns and reemerge at springs ePositive purposefully used for drainage f Negative Contamination of sinkhole can affect entire subsurface system 3 Disappearing Streams aCan inject dye to nd ultimate path in wellconnected system water can move km shr 4Various Shapes of Landscape a Natural bridge bPavement Karst blocky rectangular rocks c Haystack Ka rst d Cone Karst look like anthills e Tsingy Karst quotwalking on tiptoequot in Malagasy ex Madagascar f Tower Karst featured in many Chinese Paintings 11 Glacial Landscapes a Periglacial Geomorphology nearglacier earthformstudy of i Two Main types Mountain Valley Alpine glaciers Continental Glaciers ice sheets b Mountain Glaciers c d i Relatively small occur at higher elevations in mountainous regions ii Flow slowly downslope from zone of accumulation through zone of transport to eventual zone of ablation melting iii Zone of Accum uation 1Bowlshaped depressions on sides of mountains cirques 2Multiple cirques surrounding mountain top can create horns isolate jagged peaks and ar tes jagged ridges iv Zone of Transport 1 Glacial Valleys valleys carved by glaciers are Ushaped river valleys are vshaped 2Bigger the glacier deeper it can carve 3Movement of ice crevasses occur where glacier ows over obstacles 4Smaer glaciers feed into larger ones create hanging valleys later when ice melts waterfalls ex Yosemite 5Fjord sea level rises and oods glacial valley steep sided and deep v Zone of Ablation 1Terminus end of glacier 2Material transported by glacier is deposited in moraine pile ofjagged poorlysorted material called till 3Moraines in fjords usually limit bottomwater circulation l anoxic Ice Sheets continental glaciers i Current Greenland and Antarctica ii Greenland ice up to 3000 km thick depressed crust below sealevel iii Antarctica 2 ice sheets that meet at mountain range in middle of continent 95 of all glacial ice on Earth if melted completely would raise sea level 66m 215 ft iv Glacial erosion features 1Glacial striations long parallel scratches in bedrock caused by rocks embedded in bottom of glacier 2Glacial Polish smooth surface in bedrock caused by ner material pushed along underneath glacier rock our 3Drumlins glacier moving over hill draws it out into an elongate teardrop form pointing in direction glacier went Icelaid Deposits i Moraines composed of till 1Ground moraine deposited under glacier quothummocky topographyquot 2Terminal end moraine at furthest extent of glacier 3Recessional Moraine left behind terminal moraine during gradual retreat of glacier e 12 a 4Lateral moraine at edge of mountain glacier 5Medial moraine in between lobes of ice sheets or meeting of mountain glacier tributaries ii Erratics glaciallymoved rock that ends up on different type of bedrock 10ften kmmiles from source can map ice movement directions iii Kettle Lakes big blocks of quotdead icequot nonmoving melt slowly leaving lakes behind Minnesota Land of a thousand lakes iv Eskers long ridges of sediment deposited by streams that ran under glaciers v Moving away from glacier 10utwash plain deposited by meltwater owing from glacier 2Loess negrain material silt carried away from outwash plain by strong winds sweeping down from glacier catabatic winds aLayers can be 50100m thick approx 13 of N America has loess deposits bEx China 3Glacial Dropstones icerafted material carried by icebergs and dropped onto sea oor quotSnowball Earthquot episodes Icedammed Lakes i Glacier blocks drainage meltwater lls lower elevations adjacent to ice sheet ii Ex Glacial Lake Agassiz gt 100000 sq mi gt all Great Lakes combined iii Failure of ice dam quotIce Age MegaFloodsquot sudden hoursdays draining of glacial lake iv Glacial Lake Missoula 1lce dammed lake in Montana at end of last glacial period 13000 yrs ago ice dam ruptured 2Resulting ood gt combined ow of all rivers currently owing 3Montana produced giant ripple marks 3 stories high 4Washington stripped away regolith everything above solid bedrock cut deep channels 200 ft deep into basalt bedrock quotChanneled Scablandsquot Mineral Resources Mineral Resources i Ore deposits rocks containing minerals ofinterest at concentrations that make them economicaly worthwhile to mineextract ii Whether or not a deposit quali es as an ore depends on 1Grade degree of concentration Market Price and Technological Advances iii Factors involved in mining ores 1Exploration conditions of formation preservation concentration exposureaccessibility b Diamonds i Form at high pressuretemperature only found in mantle meteorite impacts at depth gt150 km and temp gt 1500 C ii Found in quotKimberlite Pipesquot narrow vertical injections of mantle material into crust best known Kimberlite Pipes are in South Africa Kimberly iii Use magneticelectric eld differences to nd hidden pipes c Diamond Mines and Mining i Africa 11st pipes found on DeBeers farm in South Africa 2Namibia diamonds weather out of ancient pipes that have been transported by rivers to coasts are found in beach sands and offshore deposits 3Botswana DeBeers plant at recently discovered pipe is designed so that workers never touch a gem avoid searches 4Sierre Leone pipes are located in an area controlled by quotRevolutionary United Frontquot Con ict diamondsblood diamonds ii Russia Mir diamond mine northern Siberia 12000 ft deep when mine closed 2001 2Trucks taking 90 minutes to reach surface iii Australia Argyle Mine 1Currently most productive diamond mine in the world 2Source of all pink diamonds d Gold i Precipitates with quartz in veins associated with silicic magmas ii Erosion and transport by running water concentrates gold into nuggets in placer deposits iii Process of extracting gold from ore veins uses mercury or cyanide both of which are highly toxic when released into the environment e Phosphate i Central Florida s phosphate mining district supplies gt 50 of the world s supply of phosphate for fertilizer ii Large mix of fossils can be found within deposits iii Phosphate grains 1Formed by upwelling of nutrientrich bottom water during Miocene Period ca 20 Ma 2Concentrated by subsequent winnowing via wave action
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