By far the smallest lake on this list, Crater Lake covers a mere 53
square kilometers and has a watershed of 60 square kilometers. Around
7,000 years ago, Mount Mazama of the Cascade Range underwent a huge
eruption, leaving a gaping 4,000 foot deep crater in its wake. Over
time the crater filled with debris and water from rain and runoff.
Other volcanic eruptions created Wizard Island, which resides in the
middle of the lake. Because the drainage basin is so small, it has some
of the purest water in the world.
