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– AUGUST 30, 2019
Thomas Jones’ “universal break-up criterion” won’t help with meltdowns of the heart, but it will help volcanologists study changing lava conditions in common volcanic eruptions.
Jones, of Rice University, studies the behavior of low-viscosity lava, the runny kind that’s found at most volcanoes. About two years ago, he began a series of lab experiments and field observations that provided the raw inputs for a new fluid dynamic model of lava break-up. The work is described in a paper in Nature Communications.
Low-viscosity lava is the red-hot, flowing type one might see at Hawaii’s famed Kilauea volcano, and Jones said it usually behaves in one of two ways.
“It can bubble or spew out, breaking into chunks that spatter about the vent, or it can flow smoothly, forming lava streams that can rapidly move downhill,” he said.
But that behavior can sometimes change quickly during the course of an eruption, and so can the associated dangers: While spattering eruptions throw hot lava fragments into the air, lava flows can threaten to destroy whole neighborhoods and towns.
Jones’ model, the first of its kind, allows scientists to calculate when an eruption will transition from a spattering spray to a flowing stream, based upon the liquid properties of the lava itself and the eruption conditions at the vent.
Jones said additional work is needed to refine the tool, and he looks forward to doing some of it himself.
“We will validate this by going to an active volcano, taking some high-speed videos and seeing when things break apart and under what conditions,” he said. “We also plan to look at the effect of adding bubbles and crystals, because real magmas aren’t as simple as the idealized liquid in our mathematical model. Real magmas can also have bubbles and crystals in them. I’m sure those will change things. We want to find out how.”
Jones said pairing the new model with real-time information about a lava’s liquid properties and eruption conditions could allow emergency officials to predict when an eruption will change style and become a hazard to at-risk communities.
“We want to use this as a forecasting tool for eruption behavior,” he said. “By developing a model of what’s happening in the subsurface we can then watch for indications that it’s about to cross the tipping point and change behavior.”
The study was co-authored by C.D. Reynolds of the University of Birmingham in the United Kingdom and S.C. Boothroyd of Durham University, also in the UK. The research was supported by the UK’s National Environment Research Council and Rice University.
Marina A. Yudovskaya, Gelu Costin, Vladimir Shilovskikh, Ilya Chaplygin, Matthew McCreesh, Judith Kinnaird
Textures of Bushveld chromite from thin seams and accessory disseminations in the Platreef and the northernmost Waterberg Project area were compared with textures of xenocrystic chromite from mantle xenoliths found in Neogene basalt in the Kurile Island Arc. The sieve-textured to symplectic rims around the resorbed chromite in the Kurile samples resulted from the reaction between chromite and chromite-undersaturated basaltic melt, with the inclusions in chromite being entrapped during episodes of chromite primary growth, chemical dissolution, and reprecipitation or secondary growth. The relics of the lattice-oriented etch tunnels suggest that the dissolution preferentially developed along the crystallographic planes and defects. The Bushveld chromites exhibiting similar textures are interpreted as reaction-textured chromites, by analogy with the Kurile samples. The Bushveld sieve-textured, fsh-hook to symplectic and amoeboidal to atoll-like chromites, are believed to have been formed due to coupled dissolution-reprecipitation of the earlier cumulus or xenocrystic chromite during interaction with chromite-undersaturated evolved melt. The electron backscattered difraction data confrm the same singlecrystal crystallographic orientation of all domains of the reaction-textured chromites as well as their clustered semi-dissolved relics. Therefore, Bushveld inclusion-rich chromite might have captured diferent populations of melt inclusions during its discontinuous out-of-equilibrium growth with fast episodic resorption and regeneration. The occurrence of reaction-textured chromites indicates a zone of interaction between dynamic magmatic infuxes where chemical equilibrium was not achieved whereas a complete re-equilibration between chromite and the stagnant and sequestered interstitial liquid was attained during the formation of the massive chromitites.
Yudovskaya, M.A., Costin, G., Shilovskikh, V. et al. Bushveld symplectic and sieve‑textured chromite is a result of coupled dissolution‑reprecipitation: a comparison with xenocrystic chromite reactions in arc basalt. Contrib Mineral Petrol (2019) 174: 74. https://doi.org/10.1007/s00410-019-1613-3
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