Some 586,000 acres of protected land was established by Congress in 1980 to mark the significance of Aniakchak, an extraordinary living volcano that rises to the south of Katmai. Towering more than 4,400 feet above the landscape, the volcano also has one of the largest calderas in the world, with a diameter averaging 6 miles across and 2,500 feet deep; Surprise Lake lies within it. Although Aniakchak last erupted in 1931, the explosion that formed the enormous crater
occurred before history was written. Because the area is not glaciated, geologists place the blowup after the last Ice Age. It was literally a world-shaking event. The Park Service calls it "one of the least visited units of the National Park system"—maybe a handful of people a year make it out here.
Aniakchak is wild and forbidding country, with a climate that brews mist, clouds, and serious winds much of the year; the caldera is so big that it can entirely create its own local weather patterns, and it really seems to like the bad stuff. Although the Aniakchak River (which drains Surprise Lake) is floatable, it has stretches of Class III and IV white water navigable only by expert river runners, and you must travel through open ocean waters to reach the nearest community, Chignik Bay (or get picked up by plane, along the coast). In other words, this is not something for the unprepared to try, unless you're seriously into hypothermia and have an up-to-date will. An alternate way to enjoy Aniakchak is to wait for a clear day and fly to it in a small plane that will land you on the caldera floor or on Surprise Lake. But be aware that there are no trails, campgrounds, ranger stations, or other visitor facilities here, and it is bear country; you must be prepared to be self-sufficient. Aniakchak is the world in the raw.