Topographic characterization and monitoring of volcanoes via airborne laser altimetry

Abstract

Abstract High spatial and vertical resolution airborne laser altimetry surveys of selected volcanic landforms have been used to investigate the metre-scale topographic characteristics of such features. Geodetic-quality airborne laser altimeter cross-sections of the Mount St. Helens dacite lava dome were acquired during the interval from 1987 to 1993; such data indicate that mass wasting of the flanks of the dome has outpaced episodic construction over the past seven years. Massive slumping of the south inner crater walls of the Mount St. Helens amphitheatre has been documented. Laser altimeter cross-sections of Mount Rainier have been compared with Mount St. Helens, Mount Adams, and with the Icelandic lava shield Skjaldbreidur in terms of local slope distributions, revealing basic similarities between the flanks of Rainier and St. Helens at length scales less than 5 m. When simple edifice shape parameters such as aspect ratio ( H/D ) are compared against total inferred edifice volume ( V ), Cascades stratovolcanoes such as Rainier and St. Helens fall along the extrapolation of the trend displayed for simple Icelandic lava shields. Cylindrical harmonic expansions involving laser altimeter cross-sections of volcanoes can be used mathematically to model the three-dimensional shapes of such features on the basis of only a few tens of coefficients and hence can be utilized to reduce the apparent extreme topographic complexity of major stratocones to terms that permit quantitative comparison with simpler volcanoes. In the future, geodetic airborne laser altimetry may be suitable as one of the many useful remote sensing methods for monitoring active volcanoes. A summary of the basic techniques associated with airborne laser altimetry in the context of volcanoes is provided.