GEOG 1114 1st Edition Lecture 32 Outline of Last Lecture Review of chapters 16 17 Outline of Current Lecture Review of chapter 18 19 Current Lecture Lecture 17 Ch 19 Glacial Modification of Terrain Pleistocene Ice Age Timeframe max Extent contemporary glacial extent Timeframe 2 5 million to 10 000 years ago Several interglacial periods when glaciers meted back followed by periods of advance At least five influence erosion deposition landforms Maximum Extent Almost 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 Glaciation Greenland and Antarctica 7 of oceans are ice in winter 10 of land covered by ice 22 of land covered by seasonal snow coverage and permafrost Indirect effects of Pleistocene Climate 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 ice 100s 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 Pressure As ice accumulates and compacts it becomes under pressure form overlying weight It begins to flow sliding of ice molecules one over another Capable of bending conforms to topography as it erodes State of continual flow out from center of ice sheet down valley Meltwater below glaciers due to pressure and movement lubricates glaciers Can be erratic surges inches per day Advance during years of increased accumulation Retreat during periods of reduced accumulation I Movement Flows from center down valley Oozes outward from around edges Laminar flow along edges Internal planes causing different portions to move at different speeds Basil slip bottom lubricated by water Fastest surface and in valley deeper center Effects of glaciers Erosion Transportation Deposition Erosion Plucking rock broken due to frost shattering are picked up plucked by advancing glaciers leave irregular surface Abrasion rocks picked up by glaciers scrapes and smooths the surface Transportation Glaciers carry material Meltwater under and on top of glacier carries sediments and rocks Deposition Drift any debris moved by glaciers ice and meltwater Till debris moved directly by glacier ice only rough rocky irregular debris Landforms Continental Glaciofluvial Features Mountain Continental Glaciation Features associated with ice sheets Erosion various effects Smoothing Carving lake Striation or grooves in bedrock Steepening cliffs Cutting valleys Deposition most easily identifiable Moraine mounds of till left by retreating glaciers Drumlins mounds of till reworked by later advances of ice Kettle depression left where blocks of ice were deposited then ice melted Glaciofluvial Features Outwash plain smooth flat alluvial plain deposited beyond moraines by streams issuing from the ice Eskers ridges of sand and gravel that fall our from melted water Finger lakes valleys carved out by ice sheets are filled with water to create lakes Great Lakes Mountain Glaciation Glaciers from in tops of mountains near existing stream valleys Ice flows down valley often joining other tributaries Erosion tends to steepen topography and deepen valleys Erosional 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 Ar te jagged ridge crests formed when glaciers cut into a ridge from both sides Lecture 18 Ch 18 Karst Topography and Hydrothermal Features Processes responsible for most Karst features Landforms that develop in humid areas from the dissolution of limestone Ground water solvent properties dissolve certain chemicals from rock enabling new formations How they form process of dissolution and precipitation Dominant 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 topography Occurs more rapidly in humid regions Most effective on carbonate sedimentary rocks i e limestone Results in Karst Topography Caverns and related features Limestone Caverns Large opening beneath the Earths surface that result from solation process Often found in areas with massive limestone deposits Ozark Region Stalactite hang like icicles Stalagmite form when water hits floor If they connect they re called columns Sinkholes Rounded depressions that form from dissolution of surface carbonate rock Result from the collapse of the roof of a surface cavern Wide size range Underground Streams surface runoff that is channeled on karst regions surface drainage is missing instead water seeps downward along joints Hydrothermal features such as geysers and travertine terraces Hot Springs