Please use this identifier to cite or link to this item: http://hdl.handle.net/2122/8772
AuthorsDel Gaudio, P.* 
Ventura, G.* 
Taddeucci, J.* 
TitleThe effect of particle size on the rheology of liquid-solid mixtures with application to lava flows: Results from analogue experiments
Issue Date2-Aug-2013
Series/Report no.8/14 (2013)
DOI10.1002/ggge.20172
URIhttp://hdl.handle.net/2122/8772
Keywordsrheology
magmatic suspensions
analogue model
lava flo
Subject Classification04. Solid Earth::04.08. Volcanology::04.08.03. Magmas 
AbstractWe investigate the effect of crystal size on the rheology of basaltic magmas by means of a rheometer and suspensions of silicon oil with natural magmatic crystals of variable size (from 63 to 0.5 mm) and volume fraction fi (from 0.03 to 0.6). At constant fi, finer suspensions display higher viscosities than coarser ones. Shear thinning (flow index n < 1) occurs at fi > 0.1–0.2 and is more pronounced (stronger departure from the Newtonian behavior) in finer suspensions. Maximum packing and average crystal size displays a nonlinear, positive correlation, while yield stress develops at fi > 0.2–0.3 irrespective of the crystal size. We incorporate our results into physical models for flow of lava and show that, with respect to lava flows containing coarser crystals, those with smaller crystals are expected to: 1) flow at lower velocity, 2) have a lower velocity gradient, and 3) be more prone to develop a region of plug flow. Our experimental results explain the observation that phenocryst-bearing and microlite-bearing lavas at Etna volcano (Italy) show smooth pahoehoe and rough aa’ surfaces, respectively.
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