Characteristics of Latest Eruption in the Tatun Volcano Group, North Taiwan

Volcanic eruptions used to cause huge disasters which usually bring about many fatalities and property damages, especially a big city near the volcanoes. The Taipei metropolitan city is located at the foot of Tatun Volcano Group (TVO), which has been identified as an active volcano. Meanwhile, several volcanic islands are distributed in the offshore of northern Taiwan, which may be the active volcanoes. Thus, the past eruptive behaviors and mechanisms, characteristics of products, volcanic history and activity, etc.

Based on the field observations, geomorphologic analyses, characteristics of ejecta, as well as the cases of world volcanoes, the explosive craters distributed in both sides of Chihsingshan volcano were produced by the phreatic eruption. Generally, two models of phreatic eruption have been proposed. One is a deeper hydrothermal system fed by magmatic gases being sealed and produces overpressure sufficient to drive explosive eruptions, and the other where magmatic gases are supplied via open-vent degassing to a near-surface hydrothermal system, vaporizing liquid water which drives the phreatic eruptions. The mechanism of Chihsingshan phreatic eruption is similar to the type I, which has hydrothermal reservoir underneath the volcano. Comparing other types of phreatic eruption in the world, for example, Mt. Ontake (Japan)、Inyo Craters (USA) and Tarawera Rift (New Zealand), they have similar common characteristics, (i) occurred in rifting conditions, (ii) heat source from magma intruded along the faults, (iii) had water body, such as groundwater, lakes or hydrothermal fluids, etc. near the conduit of magma. The geology and mechanism of phreatic eruption in the Chihsingshan volcano is more or less similar to the 2014 phreatic eruption of Mt. Ontake, Japan.