Wizard Island is a cinder cone of uncertain age, though it is obviously younger than the massive eruption and caldera-forming event here. Given the amount of interest and time spent studying Crater Lake, the lack of a good date surprises me. I have actually heard a park ranger tell visitors that it is the former peak of the collapsed Mount Mazama, though that was back in the 80's; that blatant falsehood seems to have been quashed more recently. The following geological map of the rocks underlying the lake is from Wikipedia. The photo was taken at Merriam point, so we're looking directly south here.