Abstract
This study presents a description of a rhyolite lava-forming eruption, including the conduit system, degassing history during the lava flow dynamics. We examined the Pleistocene Shiroyama rhyolite lava on Himeshima Island, Japan. The lava is mainly characterized by locally developed obsidian. Based on the structural variation, the obsidian lithofacies correspond to the shallow conduit. The geological investigation and FTIR analyses showed that gas removal from the conduit magma proceeded via vesiculation, fracturing, and brecciation, allowing formation of the dense obsidian. Since the lava originally maintained some extent of water, the lava effervesced just after the effusion. This vesiculation resulted in pervasive bubble coalescence and the formation of abundant permeable pathways. The volcanic gasses escaped via those pathways, allowing collapse of the bubbles and deflation of the lava. AMS (anisotropy of magnetic susceptibility) results indicate that the lava spread concentrically.
Highlights
Effusion of lava has resulted in various volcanic disasters that frequently lead to severe damage to houses, farms, and traffic networks
In contrast to the sequence proposed by Itoh [1989], our results showed that the effusion of Shiroyama lava was preceded by the activity of the Kannonzaki crater
The results of magnetic susceptibility together with geological observation indicate that the Kannonzaki pyroclastic rocks are somewhat entrained into the obsidian lithofacies at the matrix and clast scales
Summary
Effusion of lava has resulted in various volcanic disasters that frequently lead to severe damage to houses, farms, and traffic networks. Gregg 2017; Nakada et al 2019] It seems to be difficult for volcanologists to predict the flow behavior and the envisaged hazards precisely during effusion of rhyolite lava. The direct observations of rhyolite lavas are restricted to the 2008 eruption of Chaitén volcano [Castro and Dingwell 2009; Lara 2009] and the 2011–2012 eruption of Cordón Caulle volcano [Schipper et al 2013; Tuffen et al 2013] These events have provided limited but valuable opportunities for understanding rhyolite lavas [Farquharson et al 2015; Magnall et al 2018; Schipper et al 2013; Tuffen et al 2013]. Because these are infrequent events, investigation has instead generally relied on the exposure of dissected lavas and conduits, or a combination of numerical and Conduit system, degassing, and flow dynamics of a rhyolite lava
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
