A glacial ice damn filled   this basin as far as you can see.  Glaciers moved south from Canada spreading across the lake and rivers.  Glaciers advanced and retreated a dozen or more times damming up Glacial Lake Missoula, bursting with gargantuan force.  This caused flooding 400 miles away shaping today's landscape in Idaho, Washington & Oregon.     Glacial ice rose as tall as a 200 story building above     lake level.   The ice's level was 4 times as tall as Seattle's 605 ft     Space Needle.   The total depth of glacial ice may have exceeded     3,500 feet when reaching to the lake's rock bed.   Glacial Lake Missoula Only mountains with their peaks rising above 4,500 feet in elevation would have been visible from the top of the glacier.   A View From Atop The Glacier