Subglacially erupted basaltic hyalotuffs in many parts of Iceland contain sets of light-colored, resistant fins and ribs standing above the surrounding soft palagonitized hyalotuff. Our work has revealed that, although these structures look superficially like veins, they are actually deformation bands - structures that form in porous materials in lieu of through-going fractures and that allow fault-like offset along quasi-planar zones of pore space collapse and, commonly, cataclasis. Although deformation bands do occur in association with faults in hyalotuff on Reykjanes in southwest Iceland, the subglacial ridge at Valahnúkar in south central Iceland displays sets of deformation bands whose formation is clearly not fault-related. Multiple lines of evidence indicate that these deformation bands formed in unconsolidated tuff as the subglacial edifice was forming and locally collapsing as the pile accumulated. The presence of large, fragile, highly vesicular grains of basaltic glass not protected by a buffering matrix of finer grains appears to be the key to formation of deformation bands in these unconsolidated materials.
If you would like to read more about our current work, you can download our recent research poster presentations:
* 2010 GSA poster: The role of deformation bands in the collapse of subglacial hyaloclastite ridges: an example from Valahnúkar, Iceland
* 2009 GSA poster: Fragile glass: deformation band formation in unconsolidated hyalotuff, Valahnúkar, Iceland
Dr. Simon Kattenhorn, University of Idaho
Undergraduate research students
Elyse Williamson (Hamilton '10), Jane Barnes (Hamilton '09), Cody Westphal (Hamilton '08), William Hoffman (Hamilton '07)