The Columbia Icefield, at the northern end of Banff, straddles the Banff and Jasper National Park border and extends into British Columbia. Snow Dome, in the Columbia Icefield is a hydrological apex of North America, with water flowing via outlet glaciers to the Atlantic, Pacific and Arctic Oceans. Saskatchewan Glacier, which is approximately in length and in area, is the major outlet of the Columbia Icefield that flows into Banff National Park. Between the years 1893 and 1953, Saskatchewan Glacier had retreated a distance of , with the rate of retreat between the years 1948 and 1953 averaging per year. Overall, the glaciers of the Canadian Rockies lost 25 percent of their mass during the 20th century.