The North Cascades begin at Snoqualmie Pass in Washington State and end at the Fraser River in British Columbia. These mountains are a complex mixture of rock derived from dead volcanoes, live volcanoes and sediments deposited in streams and seas that dried up millions of years ago. The older rock was formed before and during the time of the dinosaurs and has been upthrust, buried, baked to the melting point and beyond, bent back on itself, rehashed reworked, recycled and then upthrust again to be carved away by glacier ice.
During the most recent geological history of the North Cascades, glaciers have been the dominant erosional force and they have created much of the landscape that is so familiar to us. The Cascade Mountains receive abundant precipitation from the nearby Pacific Ocean. In the fall, winter and early spring much of this precipitation falls as snow. If this snow falls in an area where it does not completely melt away during the warmer months, it slowly transforms into ice. When ice reaches a depth of about 50 meters (165 feet) it becomes plastic and flows somewhat like a stream, becoming a river of ice called a glacier. Erosion in these mountains has left a vertical relief ranging between 4000 feet (1220 m) and 6000 feet (1830 m). Most of the glaciers that carved the ruggedness into the Cascades were part of an immense continental ice sheet that retreated about 12,000 years ago.
Though the large ice sheets of 12,000 years ago are gone, many small alpine glaciers remain. Present day glacial activity is evident in many streams and lakes that are variously colored pea green, azure blue or chocolate brown by glacial flour, rock that has been ground into powder by the ice and is small enough to be suspended in and color the waters below a glacier.
The North Cascades have the most glaciers of any area in the lower 48 states. These glaciers are natural reservoirs for water which is important for fisheries, farming and power generation. Glaciers are the source for 25 per cent of the region’s water supply of 230 billion gallons of water each year.
Scattered among the photos in this page you might also find a few landscapes from Puget Sound or the Coast of Washington.
