Depth of the ash flow deposit in the Valley of Ten Thousand Smokes, Katmai National Park, Alaska

Abstract

In anticipation of a drill hole, seismic refraction and gravity profiles acquired more than 20 years ago have been reinterpreted in light of new density data to determine the thickness of the ash flow deposit in the Valley of the Thousand Smokes (VTTS). The data show the ash flow is at least 170m thick and most likely welded in its lower portion. Its average density is ∼1800 kg m −3 . Seismic velocities range from 0.6 to 1 km/sec for the deposit's unwelded 30‐to‐50m‐thick top section and 1.8 to 2.5 km/sec for the lower welded section. The data confirm the first realistic estimate of the volume of the ash flow of about 11 km³ by Curtis (1968), based on a geomorphic analysis of stream profiles.