Crater Lake was formed when the colapsed dome of the volcano called "Mount Mazama" filled with water from snow melt and rain, aprox. 7,700 years ago. Later eruptions created the cinder-cone island, known as "Wizard Island", seen isolated amidst the magnificent blue water. The yellow streak in the water, at the lower-left corner, is evergreen pollen.
This lake is the main feature of Crater Lake National Park. It is 5 miles at its widest point, and 1,148 ft at its deepest.