Rising from the Copper glacier, Alaska's Copper River flows through a glacier-carved landscape of steep mountains and fields of sand dunes before emptying into the Gulf of Alaska. The river is choked with silt and lined with sand. It is also prone to high winds. In this image, from 30 October 2009, the wind is blowing from the snow-covered mountains to the Gulf of Alaska. The wind picked up fine sediment from the riverbank and carried it over the ocean. The pale brown plume of airborne dust contrasts sharply with the dark ocean beneath it. The sand and silt come from the combined erosive power of flowing ice and water. Heavy glaciers grind rock into fine sediment and gravel as they flow slowly down mountain valleys. The sediment washes into rivers and streams, and much of it eventually makes its way to the Copper River. The flowing water of the river also erodes away rock, adding to the accumulation of sediment from glaciers
Photograph: Terra/MODIS/NASA
The Guardian
Comments