Journal
GEOPHYSICAL RESEARCH LETTERS
Volume 40, Issue 21, Pages 5658-5664Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1002/2013GL058105
Keywords
volcanic ash; tuffisite; porosity; ultrasonic velocity; brittle; pore-emanated crack model
Categories
Funding
- Deutsche Forschungsgemeinschaft (DFG) [LA2651/3-1]
- EU VUELCO consortium
- Starter Grant SLiM of the European Research Council (ERC) [306488]
- DFG [HE4565/2-1]
- LMUexcellent Research Professorship in Experimental Volcanology of the Bundesexzellenzinitiative as well as the Advanced Researcher Grant EVOKES of the ERC [247076]
- European Research Council (ERC) [306488] Funding Source: European Research Council (ERC)
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Sintering and densification are ubiquitous processes influencing the emplacement of both effusive and explosive products of volcanic eruptions. Here we sinter ash-size fragments of a synthetic National Institute of Standards and Technology viscosity standard glass at temperatures at which the resultant melt has a viscosity of approximate to 10(8)-10(9) Pa.s at 1bar to assess sintering dynamics under near-surface volcanic conditions. We track the strength recovery via uniaxial compressive tests. We observe that volcanic ash sintering is dominantly time dependent, temperature dependent, and grain size dependent and may thus be interpreted to be controlled by melt viscosity and surface tension. Sintering evolves from particle agglutination to viscous pore collapse and is accompanied by a reduction in connected porosity and an increase in isolated pores. Sintering and densification result in a nonlinear increase in strength. Micromechanical modeling shows that the pore-emanated crack model explains the strength of porous lava as a function of pore fraction and size.
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