International Geologiical Congress - Oslo 2008


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MPV-01 General contributions to volcanology


Volcanic characteristics of Kueishaotao, northeast Taiwan, and their implications


Sheng-Rong Song, Department of Geosciences, National Taiwan University (Taiwan)
Ching-Lung Chiu, Department of Geosciences, National Taiwan University (Taiwan)
Shuhjong Tsao, Central Geological Survey, MOEA (Taiwan)
Wei Lo, Department of Materials and Mineral Resources Engineering, National Taipei University of Technology (Taiwan)
Yu-Chung Hsieh, Central Geological Survey, MOEA (Taiwan)
Chi-Xuan Chen, Central Geological Survey, MOEA (Taiwan)


The Kueishantao (KST) is a young volcanic island located at the southernmost part of the Okinawa Trough. TL dating of siltstone xenoliths collected from the lower part of the pyroclastic deposit shows the last eruption may be younger than 7 ka. Furthermore, on-land fumaroles, active submarine hydrothermal mounds and high heat flow around this island all indicate that an active magmatic system may exist underneath it. However, there is no systematic and extensive study regarding the formation and evolution of KST.
In this study, we established a 1/5,000 geological map and mainly divided the exposed volcanic rocks into six lava flows interlayered with pyroclastic flows. In addition, based on the observation of drilling core at the northern flank and surface outcrops, it shows the KST as a typical stratovolcano with two volcanic centers which are mainly composed of lava flows, pyroclastic flows, lahars, and hydrothermal deposits. In KST, the occurrence of xenoliths is common in volcanic rocks and shows an increasing trend from the bottom of our drilling core to the top, which inferring an intensification of crustal contamination. Our investigation suggests that the possibility of volcanic eruption can not be excluded in the future and associated disasters such as ash fall and tsunami induced by the collapse of the KST volcanic edifice will have great potential to cause casualties in the adjacent area. Long-term monitoring, thus, of volcanic activities around KST should be required for future hazard assessments.


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