1GY 301: GeomorphologyGY 301: GeomorphologyLecture 21: Glaciers and Glacial Mechanics UNIVERSITY OF SOUTH ALABAMASource: Erebus_glacier_cave_NOAA_1978.jpgLast TimeGroundwater • The hydrosphere and the hydrological cycle• Groundwater concepts• Hydrogeology concepts (Darcy’s Law, 3 point problems)Hydrological CycleMost of the planet’s water is in the oceans (96%) followed by the ice caps (3%) and then groundwater (1%)http://www.coloradocollege.edu/dept/ev/courses/EV211WWW/hydrological%20cycle.jpgGroundwaterGroundwater is water that infiltrates below the Earth’s surfacePorosity: percent void space in a materialPermeability: degree of connectivity of pores (ability of a material to transmit a fluid)http://www.belmont.sd62.bc.ca/teacher/geology12/photos/erosion-water/permeability.gifWater Table Morphology• Porous layers that are capable of passing water and releasing itat springs and/or wells are called aquifers.http://www.tol.ca/files/web_images/engineering/environment/WebImages/unconfined.jpgTypes of AquifersPotentiometric Surface: elevation to which the pressurized water in a confined aquifer will riseArtesian Well: water rises to an elevation above the aquiferFlowing Artesian Well/Spring: potentiometricsurface is above the ground surfacehttp://www.douglas.co.us/water/images/Denver_Basin_Aquifers_clip_image004.jpg2Other Groundwater Issues• Ground subsidence and collapse SinkholesGroundwater Flow• Darcy’s Law: governs the volume of groundwater produced at a well headQ= A(K x h)– Q is volume – A is cross sectional area of aquifer– K is permeability– h is hydraulic head– l is map distanceli.e., you can determine groundwater flow ratesGroundwater FlowThree Point ProblemCalculate the direction of groundwater flow based upon water table elevationsWater flows from high elevations to low elevationshttp://www.uwgb.edu/dutchs/Graphics-Geol/structur/manual/fig13a.gifToday’s LectureGlaciers and Glacial Mechanics• Types of glaciers• Formation of glacial ice• Movement of iceGlaciersGlaciers are thick masses of ice that originate on land through the accumulation of snow.http://media-cdn.tripadvisor.com/media/photo-s/01/25/4a/ee/in-the-mountains-above.jpgAll that is required is for more snow to fall in the cold winter months than melts in the warm summer months.GlaciersGlaciers are thick masses of ice that originate on land through the accumulation of snow.SnowFirnGlacial Icehttp://www.ig.utexas.eduGlaciers form through a 3 step process3GlaciersGlaciers are thick masses of ice that originate on land through the accumulation of snow.SnowFirnGlacial IceGlaciers form through a 3 step processhttp://www.swisseduc.ch/glaciers/glossary/icons/firn.jpgGlaciersGlaciers are thick masses of ice that originate on land through the accumulation of snow.SnowFirnGlacial IceGlaciers form through a 3 step processhttp://pubs.usgs.gov/of/2004/1216/f/images/firn1.gifGlaciersThe transition from snow to ice results in an increase in density and a loss of porosity.http://eesc.ldeo.columbia.eduTypes of GlaciersGlaciers form in environments where it is cold.1) Polar regions: Ice Caps and Continental Glaciers2) High altitude (e.g., >10,000 feet): Alpine or Valley GlaciersTypes of GlaciersAlpine or Valley Glaciers(frozen rivers)http://www.scienceclarified.com/images/uesc_05_img0282.jpgAlpine Glaciershttp://www.scienceclarified.com/images/uesc_05_img0282.jpgAlpine or Valley Glaciers(Zone of Accumulation; Zone of Wasting/Ablation, Calving,)http://stloe.most.go.th/html/lo_index/LOcanada3/305/images/5_2.jpgChalk Board4Alpine Glaciershttp://www.scienceclarified.com/images/uesc_05_img0282.jpgComponents of Alpine Glaciers•Toe•Head•Compression Ridges•Crevasseshttp://stloe.most.go.th/html/lo_index/LOcanada3/305/images/5_2.jpghttp://farm1.static.flickr.com/91/266492544_90908ec6c0_o.jpgToeHeadhttp://www.ig.utexas.eduAlpine GlaciersComponents of Alpine Glaciers•Toe•Head•Compression Ridges•Crevasseshttp://www.ig.utexas.eduhttp://www.geo.mtu.edu/great_lakes/ice/field_photos/images/pressure_ridge3.jpgAlpine GlaciersComponents of Alpine Glaciers•Toe•Head•Compression Ridges•Crevasseshttp://cascadeclimbers.com/plab/data/509/3820Dorado0002.JPGhttp://www.ig.utexas.eduIce MovementIce moves down slope from the zone of accumulation to the zone of ablation due to a combination of plastic flow and basal slip.http://nevis.k12.mn.us/academics/science/glacier_hor_profile1.jpgIce MovementIce moves down slope from the zone of accumulation to the zone of ablation due to a combination of plastic flow and basal slip.Firn50 mIce MovementIce moves down slope from the zone of accumulation to the zone of ablation due to a combination of plastic flow and basal slip.Firn50 mFlowSlip5Ice MovementIce moves down slope from the zone of accumulation to the zone of ablation due to a combination of plastic flow and basal slip.Firn50 mFlowIce MovementIce advances down hill due to basal slip and plastic flow, but glaciers can appear to retreat if the rate of melting exceeds the rate of down slope movement.http://media.photobucket.comRhone GlacierRhone GlacierGlacial BudgetEquilibrium line: the boundary between accumulation and ablation on a glacier.Geological Effects of GlaciersIce exerts tremendous erosive force on bedrock forming unique geomorphologic features and transporting great quantities of sediment ….… to be continuedhttp://www.kschapterc.org/album-mead/23.jpgUpcoming StuffHomeworkGroundwater and Karst Geomorphology (due Friday)Next Lecture: Alpine Glacier GeomorphologyFriday’s Lab: Map interpretation (alpine glaciers)Soup