Saint Mary Lake, Glacier National Park, Montana

Early-morning storm clouds gather over Little Chief Mountain in the Lewis Range as winds roil the surface of Saint Mary Lake in this photograph of Glacier National Park, Montana. Beautiful glacier-carved lakes adorn many valleys here at the east side of the range and are often subject to strong Katabatic winds which drain down from the continental divide. As recently as 20,000 years ago at the height of the last ice advance, this valley was filled to a depth of over 1,000 feet by a large valley glacier. By 12,000 years ago, these glaciers had melted away to reveal the landscape we see today. The small glaciers which cling to high slopes along the continental divide today are the remnants of a more recent cold period. Climatologists and glaciologists estimate that Glacier Park will be virtually glacier-free within 20 years at the present rate of melting.