Matanuska Glacier is a stable 27-mile long river of ice flowing from the Chugach Mountains north almost to the Glenn Highway. With a 4-mile wide terminus close to one of Alaska's major highways, the Matanuska Glacier is the most popular roadside attraction between Anchorage and Glennallen. This glacier is a valley glacier; it exists on a valley floor.
The Matanuska is an active glacier which advances at one foot per day. It takes approximately 250 years for the ice to form upglacier and advance to the terminus. The ice of an active glacier always moves forward due to gravity; like water in a river, the ice will flow downvalley. When ice melts at a higher rate than snow accumulates, the glacier margin 'recedes'. (The term 'receding' does not refer to the ice actually travelling back up the valley.)
Whay is it so blue? The density of glacier ice allows the entire spectrum of light to be absorbed with the exception of the blue light which is reflected, and can therefore be seen by your eye.