Volcanic cities and their fire hazard

 

Tuff has been extensively used as a building material in volcanically and tectonically active areas over many centuries, despite its inherent low strength. A common and unfortunate secondary hazard accompanying both major volcanic eruptions and tectonic earthquakes is the initiation of catastrophic fires. In such a case, tuffs have commonly been regarded as resistant to high temperature exposure, but are they?

During a post-doctoral internship in the Section for Mineralogy, Petrology and Geochemistry , Dr. Michael Heap (now at the Institut de Physique du Globe de Strasbourg) and colleagues have exposed zeolite-bearing tuff, a common building material (current worldwide zeolitized tuff consumption as a dimension stone is at about 3 x 106 tons per year), as a liability in fire hazard mitigation. These thermally-unstable zeolites represent the “cement” that promoted lithification and consequently, upon their loss at high temperature, the structural integrity of the tuff deteriorates significantly. The implications of their findings are that, in the event of fire, the stability of buildings or structures built from tuff containing thermally-unstable zeolites will be jeopardized.

The study recommends that this knowledge should be considered during fire hazard mitigation and that tuffs used in construction worldwide should be tested to deduce whether they contain thermally-unstable zeolites.

These findings have been recently reported in the prestigious journal “Geology”.“How tough is tuff in the event of fire?” by Heap, Lavallée, Laumann, Hess, Meredith, and Dingwell.
http://geology.gsapubs.org/content/early/2012/03/01/G32940.1.abstract