GlaciersEarth ScienceChapter 6p. 154-159, 168-173Valley and Piedmont Glaciers• Malaspina Glacier, AlaskaSouthern HemisphereNorthern HemisphereGlacier movement, tracked by stakesCrevasseGlacial Snow BudgetIceberg PhotoStriations and polishCycle of valley glacier erosionU-Shaped Valley with tarnsHanging ValleyAreteCirque, HornFiordLateral moraineLateral and Medial MoraineMoraine deposithttp://jesse.usra.edu/articles/iceagemodule/iceagemodule-paper.htmlLoesshttp://ns.geo.edu.ro/~paleomag/Continental Glacial depositsPleistocene Ice MaximumBering land bridgehttp://www.atmos.washington.edu/~dennis/Our_Changing_Climate.htmlUpper Midwest End MorainesCoastal moraines of New EnglandUpper Midwest drainage before glaciationUpper Midwest Drainage—after glaciation• Deranged drainage after ice meltsPluvial Lakes of SouthwestIce Age Sea Level on North AmericaPast Glacial Ages• Pliocene-Pleistocene– Ice in Antarctica starting about 40 m.y.a.– Widespread N. Hemisphere ice about 3 mya– Advances every 40,000 to 100,000 years• Karoo Ice Ages– 260 to 350 mya– Lasted 90 million years– Wegener’s evidence of continental movementLocation of 300 MY Continental GlaciationLocation of 300 MY Continental Glaciationwith continents located 300 mya• Andean-Saharan Ice Ages– 430 to 460 mya– Lasted 30 million years• Cryogenian– 630 to 850 mya– Lasted 200 million years– Periods of all Earth covered with glacier• Huronian– Over 2 billion years ago– Lasted 300 to 400 million yearsPast Glacial AgesDocumentation•Drift• Loess and marine deposits• Oxygen isotope ratio in shells• Air trapped in ice—CO2levelsCauses• Land mass configuration– High latitude land mass—Antarctica– High elevation in westerlies—Andes, Cascades• Coincidence of astronomical variations of Earth in relation to Sun– Orbit shape: eccentricity– Axial tilt amount: obliquity– Tilt direction superimposed on orbit shape: progression of the equinox•CO2levels—may be effect and not causeElliptical orbitAxial Tilt variationobliquityPrecession of axial tiltMilankovitch cyclesNorthern hemisphere insolation differences due to MilankovitchcyclesOxygen isotope fractionationTemperature record from O-18Threshold diagramPositive Climate Feedback Loops• Ice albedo decreases temperature, increases ice. Reduced ice increases temperatureIce-albedo feedback loopPositive Climate Feedback Loops• Ice albedo decreases temperature, increases ice. Reduced ice increases temperature• Glacial periods result in larger arid areas, increasing delivery of iron nutrients to sea, lowering CO2levels, and temperature• Lowering sea level will expose reefs to weathering. Reaction consumes CO2, lowering temperature. Rising sea level has opposite effectNegative Climate Feedback Loop• Forest die out during glacial ages, reducing mechanism to remove CO2from atmosphere, increasing temperatureForest cover—negative feedbackTemperature compared to sulfur aerosol concentrationNutrient cycleNutrients related to sea level changeIce Age Sea Level on North
View Full Document
Unlocking...