The effusive-explosive transitions at Rokatenda 2012–2013: unloading by extrusion of degassed magma with lateral gas flow

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• 作者：Sofyan Primulyana ; Philipson Bani ; Andrew Harris
• 关键词：Rokatenda volcano ; Degassed magma plug ; Dome extrusion ; Lateral gas flow ; Unloading
• 刊名：Bulletin of Volcanology
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：79
• 期：2
• 全文大小：
• 刊物主题：Geology; Geophysics/Geodesy; Mineralogy; Sedimentology;
• 出版者：Springer Berlin Heidelberg
• ISSN：1432-0819
• 卷排序：79

文摘

Between October 2012 and August 2013, Rokatenda, one of the most poorly understood volcanoes in Indonesia, entered a phase of intense eruptive activity which involved extrusion of viscous lava, gas discharge and explosive activity. During the 10-month-long eruption, a lava volume of 2–5 × 106 m3 was extruded at mean output rate of 0.3 m3 s−1, with 2 to 3-month-long high extrusion rate phases being terminated by explosive events. Extrusion built a lava dome attaining a maximum height of ∼80 m above the crater rim, with a basal width of about 250 m. The composition of the 2012–2013 lava dome is comparable to that of the 1980 lava dome, both being andesite-trachydacite. Mineralogically, the 2012–2013 lava dome is mainly composed of plagioclase, pyroxene and an undetermined opaque mineral. Halogens released during eruption are consistent with the extrusion being fed, at least in the first eruption phase, by a degassed magma. This resulted in the formation of a dense, viscous plug in the conduit that led to a lateral gas flow, with gasses escaping around the plug to form multiple craters surrounding the dome. During the course of the eruptive activity, degassed magma was progressively forced out of the vent to unload deeper magma and force the system into an explosive phase. Such a scenario has occurred in the past at Rokatenda and is likely to be repeated in the future and creates an activity pattern that may be used to characterize such systems.