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Date Created: 12/01/14
Ch 11How Rocks Bend Tectonic forces continuously squeeze stretch bend rock into lithosphere using heat as energy Types of deformation 0 Elastic deformationrocks under low stress straindeformation is reversible O Ductile deformationhigher stress strain is irreversible O Fracturehighest stress rock will fracture Brittle vs ductile transitions determine weather the rock will fault or fold O Brittle have smalllarge region of elastic behavior small region of ductile behavior before they fracture O Ductilesmall region of elastic behavior and large region of ductile behavior before they fracture Vertical motion in the US Three types of boundaries 0 divergentoccur when two tectonic plates are moving away from each other will build ocean bw 2 chunks O convergent occur when two tectonic plates are moving towards each other continental crust moves up creating mountains and oceanic crust moves down creating trenches destroying oceanic crust O transform boundaries 2 tectonic plates move past each other causes large earthquakes 3 types of vertical faults 0 normal produce horsts and grabens blocks which sink or are exposed as neighboring blocks are pulled away 0 reversethrust result of compression for any inclined fault planeblock above the fault hanging wall block block below faultfootwall block Deformations in rocks 0 Monoclinessteplike fold in stratum O Synclinefold which dips in the middle 0 Anticlinefold which rises in the middle Five types of Folds 1 Open symmetrical Isoclinal open fold to an extreme Asymmetrical Overturned asymmetrical folds ip over Recumbent limbs of the fold become almost horizontal laying down U 39gt Ch 12Earthqaukes Three Types of Earthquakes lsubduction zone 2shallow fault 3deep Where do earthquakes happen 0 See above how deep into crust earthquakes are 0 Most occur along the edge of continental and oceanic plates Earthquake hazards O Tsunarnis create waves up to 45 miles thick 0 Ground motion ground splitting O Landslides fires 0 Liquefaction wet unlithified sediment Measurements of Earthquakes O Seismometersmeasure motion of ground vertical vs horizontal while instrument moves heavy weight remains motionless due to inertia O Richter scalemeasures amplitude height of the waves logarithmic scale ex 50 has waves ten times larger than a 40 amp generates 30 times more energy Waves of Earthquake 0 Pwavespressureprimary waves 0 Swavessecondaryshear waves cannot move through gases or liquid 0 Can figure out where Earthquakes occur by looking at PampS waves speed of waves will change depending on what they re moving through Triangulating earthquake positionsthree separate seismometers calculate the distance to earthquake s epicenter can figure out where the epicenter is beach ball diagrams show where compression and expansion occurand what kind of earthquake occured what earthquakes tell us about the corelayers O Swaves amp p waves refract and reflect when the move from one material to another 0 Colder older denser crust transmits waves faster than hotter material Ch 13Geological Time Uniformitarianismthe present is the key to the past assumption that the same natural laws that operate the universe now have always operated the universe in the past amp apply everywhere Calculations on age of the Earth 0 Kelvinestimated the time it would take for earth to cool from a molten mass to current temperatures 2040 million years 0 Usshercreation on Earth4004 BC Steno s 3 laws to determine relative ages of rock layers 0 Original horizontalitysedimentary strata are laid down horizontally O Superpositionolder strata are nearer to bottom 0 Original continuity after erosion event end up with two chunks of rock with identical layers in them but eroded rock in between themthese layers were laid down as single continuous strata but river has separted them 0 cross cuttingyounger igneous rocks cut through older sedimentary rocks 0 chemicalfossil correlation O fossil correlation depends on the principle of fossil succession groups of fossils appear in chronological order through their vertical placement in sedimentary rocks oldest found at bottom 0 chemical correlation all similar layers worldwide are the same age 0 Relative dating of rock layers 0 Radioisotope dating Ch 14 Uplift Erosion Denudation 0 Davis s 3 cycles of erosion 1 tectonic uplift creates mountains then stops 2 vertical erosion by rivers cuts steepsided vshape valleys 3 horizontal erosion by rivers widens the valleys until the whole terrain becomes at 0 Young vs Old Landscape disequilibrium O Uplift erosion occurring at same time 0 Uplift faster than erosion young landscape 0 Erosion faster than uplift old landscape 0 4 kinds of uplift l collision uplift pile up and crumbling high relief 2 isostatic uplift due to lost root two continental plates collide organic root gets scraped off and becomes lighter amp oats higher delamination 3 isostatic uplift due to hot spot terrain uplifted if hotter less dense mantle material pushes up 4 external upliftplate stretched apart by upwelling magma 0 Erosion Rates 0 Weatheringmore erosion 0 Uplift Rates 0 Warped stratacalculate how long ago the rock was laid down amp measure how far it has moved can figure out how fast the rock is moving 0 Earthquake displacementif we know often earthquakes occur in a certain location and how far they move can estimate how fast rock is moving 0 Fission track dating O when trace radioactive isotopes in a rock decay release high energy particles which tear holes and tracks fission tracks 0 below a certain temperature tracks become permanent 0 older the rock ismore fission tracks are produced 0 cosmogenic nuclideshigh energy cosmic ray interacts with nucleus producing isotopes in rocks C 14 can tell how long ago something died based on how much C14 is left 0 lichenometry geological dating that uses growth of lichen to determine age of exposed rock Ch 15 Mass Wasting 0 mass wasting downslope movement of rocks on surface driven by gravity rather than by wind water or ice ow O gravity pulls rock partly towards surface and partly along surface 0 angle of reposesteepest angle at which a pile of rock debris remains stable 0 Two kinds of rock flow 0 Slope failureslumps material moves like solid I occur when a downward and outward rotation of rock occurs along a curved surface I Top of displaced rock is tilted backwards I Exposed vertical surfacescrap 0 Rock falls rock slidesmass of rock detaches from surface and moves down I Difference is angle of surface I Downslope ows are dry granular flows I Pile the bottom of falltalus 0 How water changes the angle of repose 0 Downslope ow O Slurry owdamp soil undergoes solifluction creates characteristic lobes O Granular owless water 0 Movement in rock due to water 0 Soli uction periods of freezing and thawing slow downslope movement of watersaturated sediment O Mud owsfaster movement of wet sediment fast slurry ow 0 Freezing in Rock movement 0 Frost heavingcaused by ice lens formation layers of ice 0 Rock glacierconsist of tongue or lobe of ice segmented rock debris which moves slowly downhill in a similar manner to a glacier 0 Hazard prevention 0 Slopes can be stabilized by plastic sheeting by planting vegetation or by draining water from wet sediment O Mud ows are expected to flow down established channels Ch 16 Atmosphere wind deserts 0 Wind is caused by poleward movement which is separated into cells 0 Hadley cells at the equator warm moist air moves upward pulling cool dry air from the subtropics 0 Pacific intertropical convergence zone ITCZ one the most prominent cloud features on the planet circle the globe near the equator where northsouth east trade winds come together I Coriolis Effect 0 an idea that things get de ected to the right in northern hemisphere and to the left in the southern hemisphere 0 only effects things moving relatively slow over long distances like ocean and wind currents saltation forces grain movement in deserts shape of sand dune O sand saltates up the windward side of the dune until it forms a steep slope on the lee side 0 if lee side exceeds its angle of repose sand slips down the slip face Ergs sand seas vast tracks of shifting sand found in deserts form downwind from rivers or glacial plains Loess the deposit of windblown sediment in large amounts Ways wind can erode surfaces 0 De ationsmaller particles are picked up and moved larger rocks remain O Eventually surface consists of only larger rocks surfacedesert pavement O Abrasionwhen wind blown particles slowly wear away at the windward side of an exposed rock 0 Abraded rockventifact Desert varnishcharacteristic surface which appears on exposed and undisturbed rocks in desserts Types of Deserts 1 Subtropicalhadley cells bring very dry air 2 Continental deserts too far from any source of water vapor to get any rain 3 Rain shadow deserts occur on the lee side of mountain rages as air rises up the windward side of the mountains cools and releases moisture as it descends down the lee side warms and evaporates moisture present 4 Costal deserts western coasts of continents occur where sinking cool dry air from Hadley cells meets cold ocean currents cools them more 5 Polar desert only kind of desert which are cold caused by low moisture cold descending air KNOW FOR TEST Atacama Desert located in Chile is a costal desert driest place on Earth closest place to Mars on Earth Desertification prevention 0 Desertificationinvasion of deserts into nondesert landscapes 0 Can be caused by human activity such as draining water channels for irrigation or overgrazing of soil 0 Sand fenceshelp mitigate desertification by slowing the wind causing sand to drop out instead of spreading Ch 17Streams and Drainage Systems Drainage basinarea of lad where all of the surface water converges to a single point Runoffany water that moves across land 0 Overland flowsheets of water with no channel 0 Stream owstreams of water in channels 0 Importance of streams for cities 0 Used for transportation 0 Valley oors are at and easy to build on 0 Soil tends to be deep and fertile 0 Water is available I As river ows to sea 0 Tributaries add water to stream increase discharge downstream 0 Width and depth increase to accommodate greater water volume 0 Velocity increases to handle greater volume friction is reduced 0 Gradient steepness of channel decreases downstream 0 As base level is reached potential energy is decreased I Sea is salty because material moves along the bed of he stream by saltation 0 Types of Channels 0 Straightrare O Meanderingform in areas of low relief gentle gradients and finegrained sediment I When two curves moving toward each other meet cut off the meander and form oxbow lake 0 Braided channels channels repeatedly split and rejoin I characteristics of oods and glaciallyfed rivers I formed by periodically variable streams in areas of easily erodible material I Placer deposits 0 Stream s velocity changes from place to place down sorting occurs 0 Sorting can create concentrated mineral deposits placer deposits 0 Floods O Occur when a stream s discharge becomes so great that it exceeds the capacity of the channel 0 Hydrographa plot of river s discharge overcharge time can predict a storm causing a ood I Glacial Lake Outburst Floods O J Bretz studied channeled scablandsarea of bare basaltic bedrock in Washington state 0 Hypothesized that Channeled Scablands were created by a catastrophic ood glacial lake outburst ood 0 Formation of English Chanell is also a Glacial Lake Outburst Flood Ch 18Ground Water I Porosityamount of pore space in rock amount of water that can be stored I Permeabilityeasy with which uids ow through a rock or sediment O Controlled by grain size sorting grain shape packing O Rocks which are more porous are more permeable 0 Different rocks have different porosities amp permeability Aquifersediment or rock that tranmits water easily permeable O Unconfined aquiferdoes not have confining aquitard between it and the surface 0 Confined aquifer has a confining permeable layer deeper under the ground Aquitardsediment or rock that has a low permeability impermeable Recharge amp Discharge of ground water 0 Rechargewetlands add water to ground water system 0 Dischargewetlands take water from groundwater system Artesian water vs spring well water 0 Artesiangroundwater in aquifers that is confined under pressure will ow from a well regular well water does not undergo this pressure 0 Spring waterwater from a natural spring that flows naturally to earth s surface 0 Ground water or well water Hydraulic headelevation of the water table above a reference elevation sea level 0 Related to potential energy 0 Flow rates are controlled by the hydraulic head and the permeability of the rock Water hardness O Refers to the amount of certain metals dissolved in water usually calcium and magnesium 0 Hard water contains metal ions which can become insoluable leaves limescale and soap scum Karst landscapeformed by dissolution of soluable rocks 0 Underground drainage system 0 Weathers resistant rocks 0 Contains speleothemcave formations secondary mineral deposit Groundwater contamination O Pollutants move more easily through coarser more permeable substrates 0 Sand can immobilize it and contaminate them 0 To prevent injection wells can deposit waste in impermeable rock formations beneath aquifers 0 Well lined waste ponds can stop waste from seeping out and contaminating aquifers
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