| Abstrakt: |
Indonesia is a part of the Pacific ring of fire. The Bali Island was formed 23 million years ago due to the submarine volcanic activity. In the recent period, the island has two volcanoes and also was surrounded by volcanoes from the west and east, including Tambora. Volcanic eruptions were leaving paleo ecological traces in almost all landscapes and waters. Clay minerals are one of the proxies that significantly provide retrospective information regarding the impact of eruptions The information based on clay mineral on a short core sample in Benoa Bay, Bali, Indonesia, aimed to reveal anthropogenic and/or natural hazard signature on several decades and to provide the sedimentary environment reference in the research area. The research was deployed in March 2017; single core samples were taken using a simple core made of two inches diameter PVC pipe. X-Ray Diffraction was used to determine clay minerals' chemical properties, and 210Pb isotope was used to determine the chronological period of sedimentary layers. Based on clay mineral proxies, Benoa Bay and its surrounding areas have experienced several disasters over five decades. In the period of 1961s volcanic activity was recorded, which caused an increase in groundwater temperature. In 1984, the lacustrine environment, which was previously closed, became re-open, allowing the oxidation process to occur. In 1996 a drastic micro-climate change in a few years was indicated, which coincided with the El Nino event and became most severe in May 1997. [ABSTRACT FROM AUTHOR] |
