Stratovolcanoes – Crater Lake National Park, OR. Fly to Crater Lake, OR, and turn on the Crater Lake, OR Map overlay. The composite cone Mt. Mazama explosively erupted 7,000 years ago. Not only was most of the cone blown away, but a large depression was created as the material collapsed into the evacuated magma chamber. What is this depression called? Note the parasitic cinder cone (Wizard Island) that has developed.