Chemistry and Physics of Minerals and Rocks/Volcanology
Influence of surface clinker on the crustal structures and dynamics of 'a'ā lava flows
Article first published online: 29 JUL 2010
Copyright 2010 by the American Geophysical Union.
Journal of Geophysical Research: Solid Earth (1978–2012)
Volume 115, Issue B7, July 2010
How to Cite
2010), Influence of surface clinker on the crustal structures and dynamics of 'a'ā lava flows, J. Geophys. Res., 115, B07210, doi:10.1029/2009JB006965., , , and (
- Issue published online: 29 JUL 2010
- Article first published online: 29 JUL 2010
- Manuscript Accepted: 23 MAR 2010
- Manuscript Revised: 3 FEB 2010
- Manuscript Received: 9 SEP 2009
- lava flow dynamics;
- lava crust structures
 Surface structures on 'a'ā and blocky lavas reflect the internal flow dynamics during emplacement and also influence the dynamics of developing flows. To investigate the effects of brittle, clinkery 'a'ā flow crusts on flow dynamics and surface structures, we conducted sand and silicone laboratory experiments that simulated the advance of lava into a preexisting channelized flow with a surface crust. Experiments carried out with relatively thin crusts produced apparently ductile surface deformation structures, while thick crusts behaved dominantly in a brittle manner. Increased crustal thickness led to increased strength under compression but favored more disruption under tension, as the flow core welled up through tensile fractures, entraining crustal material. At lava flow fronts, upwelling and entrainment would increase heat losses by radiation and advection, respectively, resulting in a positive-feedback cooling loop. Fracturing caused heterogeneous crustal distribution near the flow front, which resulted in lobate flow advance, despite the absence of the viscoelastic layer that has previously been inferred as the primary control on flow advance and lobe formation. We therefore conclude that the influence of a purely brittle crust on the dynamics and surface morphologies of lava flows is more significant than often thought. All of the surface structures produced in the experiments have been observed on lavas or glaciers and many also on landslides and debris flows, suggesting the results can assist in the understanding of a range of natural flows.