Dewey Finn energy
Thank you!
Feel free to reach out with any questions! Other relevant papers: āWhat happens if we fracture or compact rocks a little bit? doi.org/10.1007/s004...doi.org/10.1002/2016...doi.org/10.5194/se-8...
The failure mode of lavaādilatant or compactantādepends on the physical attributes of the lava, primarily the porosity and pore size, and the conditions under which it deforms. The failure mode for ed...
Compare the grey signal above with the weird loop-de-loop thing here ... This kind of complex post-failure behaviourāoccurring under stress conditions relevant to the dome or shallow š edificeācould be crucial in regulating heat and mass transfer in volcanoes. Read more: šš doi.org/10.1098/rsos...
There should theoretically exist a zone in porosityāstress space where a rock can *repeatedly* switch deformation style. And loāone of our samples exemplifies this quirky behaviour. First it compacts, then dilates, then compacts, then dilates, then compacts, then dilatesā¦
In the paper we show C*ā, as described aboveācompaction ā”ļø dilation. We also demonstrate the opposite processādilation to compaction, which we refer to as Cā* (C prime star). As far as we know, we are the first to show this formally through experiments. But wait, thereās more!
Turns out, there is, but we had to look in just the right place to find it. If we plot data from Heap et al. 2015 & Farquharson et al. 2016, 2017 as the āinelastic compaction factorā (donāt ask) vs initial porosity, there is an obvious gap. Luckily, we found some samples that fit in there nicely.
Our latest paper (doi.org/10.1098/rsos...) focusses on something slightly different. Just like there are stress/strain conditions that force a rock from compactionā”ļødilation, theoretically, there should exist a range of conditions where a rock could switch dilationā”ļøcompaction. (ignore the baboons)
Beyond a threshold applied compressive stress, porous rocks typically undergo either dilatant or compactant inelastic deformation and the response of their physical properties to deformation mode is k...
Compare the two images below, one an as-collected sample of lava from Volcan de Colima, and the 2nd a sample from the same block, but having met C*ā. Itās a messāthe groundmass has been smushed into tiny fragments (compaction), but note the fracture through the centre (dilation).
...which wants to dilate. This is a well-understood phenomenon (but infrequently observed in volcanic materials), called C*ā (C star prime). The strains required to initiate this deformation mode change are really high, so the rock is pretty mashed up by the time we get there.