Katmai is famous for volcanoes, brown bears, fish, and rugged wilderness and is also the site of the Brooks River National Historic Landmark with North America's highest concentration of prehistoric human dwellings (about 900). Katmai National Monument was created to preserve the famed Valley of Ten Thousand Smokes, a spectacular forty square mile, 100 to 700 foot deep, pyroclastic ash flow deposited by Novarupta Volcano. There are at least fourteen volcanoes in Katmai considered "active", none of which are currently erupting. Brown bear and salmon are very active in Katmai. The number of brown bears has grown to more than 2,000. During the peak of the world's largest sockeye salmon run each July, and during return of the "spawned out" salmon in September, forty to sixty bears congregate in Brooks Camp along the Brooks River and the Naknek Lake and Brooks Lake shorelines. Brown bears along the 480 mile Katmai Coast also enjoy clams, crabs, and an occasional whale carcass. A rich variety of other wildlife is found in the Park as well. There is plenty room for great diversity of wildlife in Katmai which encompasses millions of acres of pristine wilderness, with wild rivers and streams, rugged coastlines, broad green glacial hewn valleys, active glaciers and volcanoes, and Naknek Lake.