GLACIERS ACTIVE AND ANCIENT OF THE PACIFIC NORTHWEST
Geology 208, Spring 2000
Joseph Hull

copyright 2000 Joseph Hull

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Active, Present Day Glaciers: valley or alpine glaciers found at high altitudes
     glaciers found in Olympics, North Cascades, all Cascade volcanoes
          too dry and warm in most of South Cascades, Okanogan, etc.
     most glaciers fairly active with large deposits and withdrawals, fast movement
          large valley glacier will process most ice in decades
     glacial budgets negative over last 500 years or so, but few quantitative studies
          most glaciers retreated substantially from 1500's to 1950's
               positions determined from well preserved glacial moraines = till ridges
          short period of readvance on many glaciers from 50's to 80's
               must reflect some event decades? earlier.  what are response times???
          most glaciers in retreat over the last couple of decades, many have disappeared
               e.g. Paradise Glacier and its ice caves, now gone.
               big implications for hydropower, irrigation, streamflows for salmon, etc.
     some famous glaciers (we have many, lots of snowfall even though warm in WA)
          Blue Glacier on Mt. Olympus in Olympics, very well studied by UW
          Nisqually Glacier on Mt. Rainier, also well documented
          South Cascade Glacier in North Cascades, focus of much investigation

Wisconsin Glaciation approximately 20-10,000 years ago
     two enormous ice sheets covering North America, western sheet = Cordilleran
          Puget Lobe of Cordilleran extended past Olympia to Mima Mounds near Rochester
               left giant slug track of moraines, drumlins, outwash, etc.  sand, gravel, till, clay.
                glacial lakes way out in front, outwash in front of glacier, till underneath
                advancing glacier produces vertical succession of glacial related deposits
                    Vashon clay under Esperance sand under Lawton till
           Puget Lobe crossed US border about 18000, back across about 10,000 yrs b.p.
                1000 m of ice over Seattle at glacial maximum
          Okanogan Lobe of Cordilleran extended down into northeast Cascades
          Purcell Lobe of Cordilleran extended down into northern Idaho and w. Montana
               temporarily blocked Clark Fork River draining out of Montana into Columbia
               dammed river, created giant glacial Lake Missoula, "Great Lakes" volumes
               ice dam floated, released water instantly in giant floods covering entire E. WA
               floods scoured giant channels = coulees.  giant ripples on coulee floors
                    Grand Coulee, Moses Coulee, Frenchman's Coulee:  now all dry
               also created huge waterfalls/cataracts at ends of coulees, now all dry
                    Dry Falls, Cellilo Falls, etc.
               floods stripped loess = wind blown silt off bedrock, creating scablands
               floods carved giant canyon of the lower Columbia River below Wallula Gap
 

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