Our first view of Crater Lake when we arrived! It should really be the 8th Wonder of the World. Crater Lake was formed when Mount Mazama blew its top almost 7,000 years ago. The caldera walls rise 500-2,000 feet above the surface of the lake, and the diameter of the lake is 6 miles. The intense blue color is due to its purity and the depth of the caldera. It is the deepest lake in the US at 1,942 feet deep. The water has accumulated by rain and snow melt only. Visibility measurements have recorded reaching depths of 325 feet.