Glaciers and Glacial Processes Dr Ponette April 17 2014 Glaciers 10 of Earth Geomorphic Agents Also known as rivers of ice glaciers are large masses of ice flowing and sliding downslope or down a valley as a result of the pull of gravity There are two types 1 Continental Occur at areas of high latitudes and flow radially outward from the center Greenland Antarctica 2 Alpine Found at areas of high altitude mountainous regions U S Rockies Kenya Peru Flow down slope under the force of gravity Cirque valley piedmont Ice Sheets 50 000 sq km Ice Caps 50 000 sq km Glaciers Influence global climate 1 2 Good indicators of current climate 3 Long term storage of freshwater 4 Used to study past climates Influence Global Climate 1 Radiation Budget 2 Ocean Salinity Influence albedo Thermohyline circulation giant conveyor belt o Satellite imagery shows this over time Indicate Current Climate Glaciers are melting Store Freshwater Frozen freshwater Serve as Climate Proxies o How much 70 of the 3 freshwater is stored in glaciers Ash gas animal fossils and other particles get trapped in the ice Through ice cores these particles can be studied to show past climates The Principal of Superposition tells us that the younger layers are positioned on top of the older layers Where do Glaciers Occur There are glaciers on every continent except for Australia Glaciers are found at areas of high latitude and high altitude 96 of the ice on Greenland and Antarctica is in the form of glaciers Glacier Formation Similar to how sediment turns into sedimentary and then into metamorphic rock o Snow Firn Ice o Snow Fallen Snowflakes get buried and accumulate o Firn compacted into granular ice o Ice re crystallization into ice from pressure Requires precipitation and freezing temperatures Accumulation Ablation Accumulation mostly snowfall addition of ice Ablation mostly melting loss of ice When glaciers cover more land sea level drops Continental glaciers flow radially There are glaciers near the equator o Alpine glaciers How Glaciers Flow Plastic Deformation Increasing accumulation and pressure of ice causes ice to become plastic and to flow downwards or outwards Plastic something that can be shaped and molded Basal Sliding melting at base of glacier reduces friction and pressure Glacier slides downhill Crevasse fractures in ice Flow causes stress o Tension stress o Compression stress Glaciers can flow up to 10 km per year 30 meters per day Speed of flow depends on 1 Temperature 2 Slope Stickiness Ice Thickness 3 Movement of a Glacier through melting as well as Evaporation Liquid to Gas Sublimation Solid to Vapor Calving Chunks of ice breaking off at the edge of the glacier Equilibrium line area where accumulation zone and ablation zone meet Glaciers shape the landscape through 1 Erosion 2 Transportation 3 Deposition Alpine glaciers always flow downslope We call it a glacial advance if accumulation ablation We call it a glacial retreat if accumulation ablation Plucking ice freezes onto rock and sediment and incorporates material into flow Cirque Steep sided hollow at the head of a valley formed by a glacier Horn 3 or more cirques meet at a mountain summit Till Sediment deposited by moving ice Depositional Landforms Moraine ridges of till along the margins of glaciers along the side at the toe in the middle U shaped Valleys shaped by fluvial processes V shaped Valleys shaped by glacial processes
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