The towns of Kent, Sumner, Auburn and Puyallup are built on top of the flow. This last eruption left a northeast facing depression on the mountain nearly 2 miles in diameter. About 1,000 years ago was the most recent large eruption, and about 150 years ago a small eruption occurred. Since the volcano is still active, only time will tell when Mt. Rainier might erupt again, changing the face of the landscape. The current highest peak is 14,410 feet at Mt. Rainier's summit.
Glaciers shape the park.
They are formed because the mountain's winter snowfall surpasses the snowmelt. Glaciers are rivers of ice because they move down the mountain valleys slowly, their ebbing and flowing caused by climatic conditions. Mt. Rainier's glaciers move from one to two feet per day. More than 34 square miles of glaciers radiate out from the summit. The mountain has 25 named glaciers and 50 small, unnamed glaciers and ice fields.