Analysis of the Exterior Ballistics of Block Ejecta at Nanwaksjiak Crater, Nunivak Island, Alaska

摘要

Nanwaksjiak Crater, a quaternary maar on Nunivak Island, Alaska, has a well-exposed ejecta blanket of ash and blocks ejected from the crater. Analysis of the distributions of the blocks provides clues to the internal flow conditions of the eruption. Methods of ballistics are applied to field data to determine block ejection velocities. Effects of atmospheric drag, block shape, launch angles, and wind on ballistic trajectories are discussed. Graphs are presented to allow determination of ejection velocities if size, launch angle, and range of the blocks are known. Block velocities are applied to two models for the interior flow in erupting maars to estimate flow parameters of the erupting medium. (Author)