Conduit system, degassing, and flow dynamics of a rhyolite lava: A case study of the Shiroyama lava on Himeshima Island, Japan
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...
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doaj-593d84e802874b6ea0696977124132b32021-07-16T14:01:38ZengVolcanicaVolcanica2610-35402021-07-014210713410.30909/vol.04.02.10713490Conduit system, degassing, and flow dynamics of a rhyolite lava: A case study of the Shiroyama lava on Himeshima Island, JapanKuniyuki Furukawa0https://orcid.org/0000-0002-8296-545XKoji Uno1Yu Horiuchi2Shintaro Murohashi3Motohiro Tsuboi4Aichi UniversityOkayama UniversityOita Himeshima Geopark Promotion Office Okayama UniversityKwansei Gakuin UniversityThis 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.https://www.jvolcanica.org/ojs/index.php/volcanica/article/view/106rhyolite lavaobsidiandegassingftiramshimeshima |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Kuniyuki Furukawa Koji Uno Yu Horiuchi Shintaro Murohashi Motohiro Tsuboi |
spellingShingle |
Kuniyuki Furukawa Koji Uno Yu Horiuchi Shintaro Murohashi Motohiro Tsuboi Conduit system, degassing, and flow dynamics of a rhyolite lava: A case study of the Shiroyama lava on Himeshima Island, Japan Volcanica rhyolite lava obsidian degassing ftir ams himeshima |
author_facet |
Kuniyuki Furukawa Koji Uno Yu Horiuchi Shintaro Murohashi Motohiro Tsuboi |
author_sort |
Kuniyuki Furukawa |
title |
Conduit system, degassing, and flow dynamics of a rhyolite lava: A case study of the Shiroyama lava on Himeshima Island, Japan |
title_short |
Conduit system, degassing, and flow dynamics of a rhyolite lava: A case study of the Shiroyama lava on Himeshima Island, Japan |
title_full |
Conduit system, degassing, and flow dynamics of a rhyolite lava: A case study of the Shiroyama lava on Himeshima Island, Japan |
title_fullStr |
Conduit system, degassing, and flow dynamics of a rhyolite lava: A case study of the Shiroyama lava on Himeshima Island, Japan |
title_full_unstemmed |
Conduit system, degassing, and flow dynamics of a rhyolite lava: A case study of the Shiroyama lava on Himeshima Island, Japan |
title_sort |
conduit system, degassing, and flow dynamics of a rhyolite lava: a case study of the shiroyama lava on himeshima island, japan |
publisher |
Volcanica |
series |
Volcanica |
issn |
2610-3540 |
publishDate |
2021-07-01 |
description |
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. |
topic |
rhyolite lava obsidian degassing ftir ams himeshima |
url |
https://www.jvolcanica.org/ojs/index.php/volcanica/article/view/106 |
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