Explosive or Detonative Phase Transitions on a Geological Scale

Abstract

IN both the geological and chemical literature^1–6 the possibility has been suggested that rapid polymorphic transitions provide a source mechanism for medium to deep focus earthquakes. The properties, and in particular the sign of the volume change, of “laboratory scale” rapidly phase transforming systems have not previously been considered with a view to providing further information on the proposed geological systems. There are a number of reported cases, some of which^7–17 are listed in Table 1, of transitions from a metastable state to a stable state accompanied by acoustic phenomena or shock waves. The sign of the density change during phase transition may be either positive (for example, crystallization of nickel⁸) or negative (for example, the phase change of explosive antimony^10,11).