Pahoehoe and aa lavas: a discussion and continuation of the model of Peterson and Tilling

Abstract

The graphical method of Peterson and Tilling for representing the behaviour of a lava flow is considered in terms of simple rheological theory, assuming that a lava may be approximately described as a Bingham fluid. This approach helps resolve an apparent anomaly in the original treatment of Peterson and Tilling with respect to the representation of the pahoehoe to aa transition. It also suggests further methods for quantitatively defining the limits of the pahoehoe and aa fields, and the transition threshold zone.