National Geographic : 1951 Jun
835 )on ('. Knudsen from Frederic Lewis Summer Pulls Winter's Icy Plug; Lake George Carves a Channel Through Knik Glacier Strange quirks of geography still lie hidden within Alaska's remote ranges, a surviving stronghold of the ice age. Lake George, one of these wonders, discharges its contents automatically, as if Nature had equipped it with a safety valve. Crevassed Knik Glacier (left), creeping toward the Knik River, dams the lake's outlet most of the time (page 838). Each year the lake traps enough rain, melted snow, and glacial seepage to fill a depression 15 miles long and 5 miles wide to a depth of some 200 feet. In July and August, when the lake grows brimful, a trickle of water seeps across the ice barricade. Quickly, the flow scours out a 7/-mile-long channel through a glacier 250 feet deep. Racing down the gorge, floodwaters swell the Knik Valley to a width of 2 miles. Eventually they reach Cook Inlet (map, page 840). This annual flood continues a week or more, until the lake bed becomes a mudhole filled with stranded icebergs. When cold weather returns, the glacier again seals the lake. Summer sees the hollow refilled and the washbowl effect repeated. Alaska enthusiasts, boosting the lake as a natural wonder rivaling Niagara Falls and the Yellowstone geysers, foresee the day when it will attract summer visitors by the thousands, but thus far few eyes have witnessed the spectacle. No highways, only treacherous, almost impassable trails, lead to the lake. A light plane offers the easiest transportation. Lake George lies within 25 miles of the fertile Matanuska Valley. Anchorage, the Territory's largest city (population 11,000) is 45 miles distant. This picture shows the ever-widening channel, here some 70 feet deep, squeezed between impervious mountain and yielding glacier. Undermined, enormous blocks of ice regularly break off and crash resoundingly into the torrent. When the water recedes, the glacier moves up snug against the mountain. The following pages show other sights pictured by a party of Anchorage men who flew in to record sound effects of the ice dam's breakup.