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Glacial I - Started November 1st 2011 Things you have to do...

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Unformatted text preview: Started November 1st, 2011 Things you have to do! Read Chapter 16: Glaciers, Glaciation and Permafrost Answer these questions: What information regarding global climate change can be obtained from ice cores? Where is Lake Vostok? Announcements! Labs this week in Map Library Mills Come prepared with notes, calculator etc. New Schedule: Nov 1 - Frozen World: Glaciers Nov 3 - Careers talk Nov 4 - Video- Queens of Diamonds Nov 8 Glacial Sediments & Erosion Nov 10 Groundwater/landfill Things you had to do! Answer this question: What are gas hydrates? - Methane trapped in ice crystals - Found in polar environments (oshore Vancouver Island) - Alternative energy source Earth/Envir Sc 1G03 Earth & the Environment THE FROZEN WORLD Glacier formation and movement Outline 1. 2. 3. 4. 5. Introduction Formation of ice Movement of ice Glacier budgets Classification of glaciers 1. Introduction Why are glacial deposits environmentally significant in Canada? 20,000 years ago -- 90% of Canada covered by ice (10% is up north where it is dry and not moist enough to create glacial ice) glacial deposits underlie major urban centres need to understand deposits for construction, water supply, waste, mineral exploration Fig. 16.33 2. Formationbackground of ice glacial ice is blue like Snow accumulates, compacts, melts and refreezes - changes into FIRN *know this term Firn snow which has survived a summer melt season and has begun to change into ice - similar to glacial ice except many more air pockets Firn compacts, melts and refreezes further and transforms into ice Fig. 16.4 3. Movement of ice What makes glacier ice move? - Gravity Alaska Ice moves in response to STRESS Movement or deformation of ice is called STRAIN How quickly does glacier ice move? - 3 - 300 m/yr What determines how quickly ice moves? - slope of glacier - ice thickness - temperature How do glaciers move? Basal sliding - requires water at ice base - need 'warm' ice (close to 0ºC) - ex; Alaska, Rockies Alaska Fig. 16.8 How else does ice move? Internal deformation - ice deforms as a plastic material Ice also moves by... Crevassing - upper surface of ice is brittle - fractures, or crevasses form to allow movement glaciers? ), warm temps high elevation (big slopes - Alaska, Rockies - 'warm' glaciers (where ice is close to 0ºC) Slowest glaciers? - Antarctica - 'cold' ice Where in a glacier does ice move fastest? - In the centre, at the top Ogives - dirt bands in ice - show dierential movemnt * clean bands are from winter; dirty bands in summer slow fast slow 4. Glacier budgets Relationship between gain and loss of mass - if more mass GAINED than lost (positive budget) - glacier terminus will ADVANCE - if more mass LOST than gained (negative budget) glacier terminus will RETREAT saskatchewan glacier athabasca glacier Glacier budgets Mass gained in the ACCUMULATION area Mass lost in the ABLATION (wastage) area copper mine Equilibrium line (snow line) - Point on the glacier where there is neither gain or loss of mass edge of fresh snowfall Equilibrium line Ice flow Ice flows from accumulation area to ablation area Fig. 16.6 - never flows 'backwards' 1957 South Cascade Glacier, Washington - ice front has retreated due to increased melt - ice has NOT moved backwards!! 1980 5. How do we classify glaciers? Continental ice sheets Antarctic, Greenland Laurentide Ice Sheet Ice caps - smaller than ice sheets - often in mountainous areas Vatnajokull, Iceland volcanic crater Patagonian Ice Cap Outlet glaciers - radiate from the edge of an ice cap e.g. Breidamerkurjokull, Iceland Valley glaciers - Flow in bedrock valleys e.g. Athabasca glacier could be an outlet glacier confined by walls of valley Piedmont glaciers - Valley glaciers that extend out onto lowlands Malaspina glacier, Alaska Childs glacier, Alaska Cirque glaciers - Occupy small, semi-circular hollows in mountainous regions e.g. Rockies, Alps Ice shelves - Floating part of ice sheet or ice cap e.g. Ross Ice Shelf, Antarctica Things you have to do! Read Chapter 16: Glaciers, Glaciation and Permafrost Answer these questions: What information regarding global climate change can be obtained from ice cores? Where is Lake Vostok? ...
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