GEOG 1114 1st Edition Lecture 32Outline of Last Lecture Review of chapters 16-17Outline of Current Lecture Review of chapter 18 & 19Current Lecture Lecture 17 Ch. 19 - Glacial Modification of TerrainPleistocene Ice Age: Timeframe; max. Extent; contemporary glacial extent Timeframe2.5 million to 10,000 years agoSeveral interglacial periods when glaciers meted back followed by periods of advanceAt least five – influence erosion, deposition, landformsMaximum ExtentAlmost all of North America is covered all along the Andes in South America, Northern Russia and all of Antarctica. Accumulation movement melting and formation of glaciers had enormous effect on topography and drainage. Periglacial zone- zone where ice never existed but glacial factors affected the landscape such as erosion from ice melt, solidification (soil creep in tundra)Sea-level changes – buildup of ice on continents led to less drain water on continents and brought about a lowering of sea levels (Bering land bridge)Crustal Depression- the weight of the ice on the continents caused continents to sink, ice melt allowed for continental rebound (isotasy)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Pluvial (increased rain) developments – considerable run-off results increased moisture, leading to increased precipitation and less evaporation. Think Great Salt lake- remnant of Lake Boneville.Contemporary GlaciationGreenland and Antarctica 7% of oceans are ice in winter10% of land covered by ice22% of land covered by seasonal snow coverage and permafrostIndirect effects of PleistoceneClimate change related to contemporary glaciation: retreating of polar ice caps. Shrinking ice caps an indicator of a warming climate. Antarctic ice shelves breaking. Higher flow rates of outlet glaciers.Glacial formation and movement: 2 types (Continental / Mountain); How they are formed; process of movement (pressure & flow)Continental – exists in non-mountainous areas. During Pleistocene they were vast blankets of ice100s or 1000s of meter think-thickness in interiors; thinner at outer edge. Antarctica and Greenland only two today. Outlet glaciers; ice shelves, ice burg. Ice sheets third most extensive feature on the planet- Development and flow of ice sheets: Pleistocene ice sheets originated in mid-latitudes and sub polar regions. Ice flowed outward from center of accumulation. Mountain – Highland Fields: ice accumulates in unconfirmed sheets in high mountain areas. Highland fields are outlets from valley glaciers. Alpine Glaciers: glaciers that develop individually in mountains. Cirques: small alpine glaciers confined to small basins. Piedmont Glacier: leading edge of valley glacier reaches a flat area.PressureAs ice accumulates and compacts it becomes under pressure form overlying weightIt begins to flow – sliding of ice molecules one over anotherCapable of bending – conforms to topography as it erodesState of continual flow – out from center of ice sheet – down valleyMeltwater below glaciers due to pressure and movement – lubricates glaciersCan be erratic surges – inches per dayAdvance during years of increased accumulationRetreat during periods of reduced accumulation.I. Movement Flows from center down valleyOozes outward from around edgesLaminar flow along edgesInternal planes – causing different portions to move at different speedsBasil slip – bottom lubricated by waterFastest – surface and in valley – deeper center Effects of glaciers: Erosion; Transportation; DepositionErosionPlucking – rock broken due to frost shattering are picked up (plucked) by advancingglaciers – leave irregular surfaceAbrasion – rocks picked up by glaciers scrapes and smooths the surfaceTransportationGlaciers carry materialMeltwater - under and on top of glacier - carries sediments and rocksDepositionDrift – any debris moved by glaciers (ice and meltwater)Till - debris moved directly by glacier ice only - rough, rocky irregular debrisLandforms: Continental; Glaciofluvial Features; MountainContinental Glaciation – Features associated with ice sheetsErosion – various effectsSmoothingCarving – lakeStriation or grooves in bedrockSteepening cliffsCutting valleysDeposition – most easily identifiableMoraine – mounds of till left by retreating glaciersDrumlins – mounds of till reworked by later advances of iceKettle – depression left where blocks of ice were deposited then ice melted Glaciofluvial FeaturesOutwash plain - smooth flat alluvial plain deposited beyond moraines by streams issuing from the iceEskers – ridges of sand and gravel that fall our from melted waterFinger lakes – valleys carved out by ice sheets are filled with water to create lakes – Great LakesMountain GlaciationGlaciers from in tops of mountains near existing stream valleysIce flows down valley often joining other tributariesErosion tends to steepen topography and deepen valleysErosional Features:Cirque – bowl shaped depression in mountain peak carved out by ice Horn – pyramid shaped peaks left when cirques are cut back into a mountain peak from 3 or 4 sides Arête – jagged ridge crests formed when glaciers cut into a ridge from both sidesLecture 18 Ch. 18 - Karst Topography and Hydrothermal FeaturesProcesses responsible for most Karst features.-Landforms that develop in humid areas from the dissolution of limestone. Ground water solventproperties dissolve certain chemicals from rock, enabling new formations. How they form; process of dissolution and precipitationDominant mineral is calcite (CaCo3), which dissolves in slightly acidic water crating a carbonate solution that dissolves the limestone.This dissolution of limestone by carbonic solution at both the surface and subsurface results in karst topographyOccurs more rapidly in humid regionsMost effective on carbonate sedimentary rocks (i.e. limestone)Results in Karst TopographyCaverns and related featuresLimestone Caverns: Large opening beneath the Earths surface that result from solation process. Often found in areas with massive limestone deposits, -Ozark RegionStalactite – hang like icicles.Stalagmite – form when water hits floor. If they connect they’re called columnsSinkholes – Rounded depressions that form from dissolution of surface carbonate rock. Result from the collapse of the roof of a surface cavern. Wide