Geomorphological Reconstruction of the Pre-Caldera Edifice of Raung Volcano, East Java, Indonesia
Firman Sauqi Nur Sabila, Mirzam Abdurrachman, Asep Saepuloh, Idham Andri Kurniawan

Geological Engineering Study Program, Faculty of Earth Science and Technology, Institut Teknologi Bandung, Jl. Ganesha No. 10, Bandung 40132, Indonesia

Abstract

Mount Raung is a stratovolcano with a 2.2 km wide caldera with an unknown eruption history. This volcano, located in East Java, Indonesia, is one of the most active volcano in Indonesia and became the highest (+3344 masl), youngest, and most active volcano growing on the southwest flank of the Ijen Volcano Complex. The summit of this volcano is devoid of vegetation and has a truncated cone morphology which represents a caldera with a depression as deep as 500 m. As a stratovolcano, the peak of this volcano is estimated to be higher before the caldera-forming eruption occurs. The information of original morphology of this volcano is important to interpret the pre-caldera eruptive activity. Therefore, this research was conducted to reconstruct the morphology of the Mount Raung pre-caldera edifice. The reconstruction using a basic volcanic geomorphological principles in stratovolcano type. The model of the original morphological condition of Mount Raung edifice before the caldera was formed was carried out using digital elevation model data. Reconstruction of the top of the volcano is done by drawing lines based on the ridges on the caldera slope which represent the original topography that has not been eroded. The ridges that have been obtained using tracking with the Global Mapper software are then displayed in an elevation-to-distance plot. The results of the plot are then drawn using a regression method to obtain an estimate of the peak point. A total of eight ridge lines were analyzed to obtain eight forecast points for the summit position. Based on these points, contour lines are then made which are then converted into a DEM of the top of the volcano edifice. Based on the reconstruction, the pre-caldera summit height of Mount Raung was obtained about 3761 masl. The generated paleotopography of pre-caldera has been used to calculate the volume of the lost materials. Accordingly, we calculated that the lost volume of the caldera-forming eruption is about 1.28 km3.

Keywords: Raung, Geomorphology, Edifice, DEM, Pre-Caldera.

Topic: Solid Earth Sciences