MAGMA DYNAMICS STUDY OF ANAK KRAKATOA'S VOLCANO EFFUSIVE ERUPTION PRODUCTS

• Main Author: Ismail, Taufik
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/74844
• Institution: Institut Teknologi Bandung

Anak Krakatau Volcano is an active volcano in Indonesia and has the potential to erupt on a large scale in the future. This volcano has varying resting times, namely 1 – 5, 44, 203, and 1145. Previous studies have studied a lot of volcanostratigraphy and petrogenesis of volcanic rocks of Anak Krakatau Volcano, but no one has studied specifically study of magma dynamics with method used in this study. This study is devoted to studying the dynamics of the magma that controls the effusive eruption of Anak Krakatau Volcano. The study of magma dynamics tries to study the processes that occur in deep magma chambers to shallow magma chambers to magma processes in volcanic pipes. The methods used to study the characteristics of magma are micro-texture analysis, mineral assamblage, crystal size distribution, relative viscosity analysis, decompression rate analysis, and geochemistry including major elements and an plagioclase. This study, studied 13 lava units taken from the Khuluk period of Anak Krakatau Volcano. Prepared samples were then photographed using a 4X magnification polarizing microscope. Apart from using a polarizing microscope, the prepared samples were also analyzed using a Bruker M4 Tornado plus micro-XRF and X-ray Fluorescence (XRF) tool. The other software used in the analysis is ImageJ, CSDcorrections, Microsoft Excel, and Bruker Nano Analytics. Based on CSD analysis, two segmentation crystal distributions were found, namely phenocrysts and microphenocrysts. Residence of phenocryst magma has a range of 75 – 240 years with an average value of 135 years, this shows similarities to residence time of Anak Krakatau Volcano. Relationship between magma storage time, crystallinity, decompression rate, and relative viscosity generally has the same pattern. Plagioclase microtexture in the effusive product of Anak Krakatau Volcano shows the processes that occur in deep magma chambers and shallow magma chambers leading to eruption. Magma dynamic process of Anak Krakatau Volcano from 1973 to 2017 has three cycles and twice the supply of new magma injection from partial melting or mantle plume.