GEO 155 1st Edition Lecture 21 Last Lecture Streams as Geomorphic Agents Outline of Current Lecture I Glaciers a How they form and move b Erosion and Deposition c Land forms of continental glaciation Current Lecture Formation and Movement Cold snowy winters Cool summers Net accumulation of snow squeezes air out of cracks until it turns to ice heavy weight of ice causes it to deform and move out from under the pressure o Takes at least 60 feet of ice to start moving o Known as the zone of accumulation o Might move out advance of this area into an area without net accumulation Known as the zone of ablation o Boundary between the two zones is known as the equilibrium line If this boundary shrinks the glacier retreats or recedes o Occurs at high latitudes and altitudes 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 Pleistocene During the Pleistocene Ice Age that occurred 2 5 million to 11 000 years ago a continental glacier covered most the North America Alpine glaciers covered the mountains Relic land forms covered the landscape and were leftover when the ice passed Glacier Geomorphology Plucking rock holds onto cold glacial surface and freezes to it glacier moves and pulls the rock out if the rock is weaker o Most effective area of the rock to pull from is an area with many cracks o The more a glacier erodes the better it gets at eroding due to the accumulation of rocks creating a rough friction bottom After causing erosion the glacier transports the eroded material it then deposit this material known as glacial drift in the zone of ablation o There are two types of glacial drift namely Glacial till deposited by melting ice and material is unsorted Accumulation of till is moraine Outwash reworked by melted water and material is sorted Land Forms from Continental Glaciation Erosion Ice scoured plain o Flat o Thin soils o Mainly lakes due to plucking Deposition Generally flat Terminal moraine end of glacial ice Recessional moraine new ridge forms from melting at warmer areas o Deposited when glacier was retreating Ground moraine layer of till that is flat because the ice did not stay long enough for much accumulation Drumlins steep wide hill of ice that narrows at the end of the ice s path Kame when there is a hole in the ice water runs in sediment that it carries piles up in the hole ice melts leaving a pile of sediment known as kame Esker stream runs in a tunnel within ice but there is not enough energy to move all of the sediment so it piles up when the ice melts it leaves behind a long winding ridge in the shape of the stream s path known as esker Kettle at the edge of the glacier deposited till collects a block of ice from the glacier that broke off more till collects around it while it melts a depression is created in the moraine known as a kettle
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