Arctic stream and delta, aerial photograph. This stream flows over permafrost ground, with mountains and ice and snow seen in the background. A delta is the deposition of alluvial sediments at the mouth of a river or stream, forming the characteristic fan shape seen here. The sediments consist of rock eroded by water from further upstream, as well as rock debris formed by glacial action. The water (bottom) has the colour typical of water to which rock flour, silt formed by glacial action, has been added. Photographed in Svalbard, an Arctic archipelago governed by Norway.