the core of the national monument lands encompasses the wide aniakchak crater. the high point on the caldera rim is aniakchak peak. the lake within the caldera, surprise lake, is the source of the aniakchak river. multiple streams and rivers within the caldera flow into surprise lake to form it. in addition to surprise lake, the other prominent feature inside the caldera is vent mountain, the site of the most recent (1931) eruption within the caldera. the preserve lands flank the monument on either side. subsistence hunting is allowed in both the monument and preserve, and sport hunting is allowed in the preserve. the region was virtually unexplored until the 1920s, when exploration for oil brought reports of an un-described volcano. a moderate eruption in 1931 forming vent mountain resulted in significant publicity, spurring studies to declare the region a national monument. it was not until 1978 that a monument was proclaimed by president jimmy carter under the antiquities act. the monument and preserve were established within their final boundaries in 1980 with the passage of the alaska national interest lands conservation act.