STUDY OF TSUNAMI DEPOSITS OF ANAK KRAKATOA VOLCANO ON DECEMBER 22ND IN BATU HIDEUNG, TANJUNGJAYA, PANIMBANG, PANDEGLANG, BANTEN PROVINCE

• Main Author: NURJENNAH, SITTI
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/52901
• Institution: Institut Teknologi Bandung

Anak Krakatoa Volcano erupted on December 22nd, 2018, cause a flank collapse on the body of Anak Krakatoa. The flank collapse triggered a tsunami in the Sunda Strait. One of the areas affected by the tsunami is Batu Hideung which was used as a research site. Research about tsunami deposits caused by volcanic collapse is still limited and most of the studies that have been conducted have focused on the tsunami deposits by the earthquake. The study aims to determine the characteristics of tsunami deposits caused by a flank collapse based on megascopic observations, foraminifera content, grain size (granulometry), chemical element content, and cluster analysis. Besides, this study also compared the characteristics of tsunami deposits cause a flank collapse, earthquake, and storm deposits. The research was conducted on 53 samples with the code TJL at 8 location points derived from a one transect trajectory in Batu Hideung. This research was a part of research from The Indonesian Institute of Sciences’ Geotechnology Research Center. The characteristics of tsunami deposits are obtained by conducting megascopic observations, foraminifera content, grain size, chemical element content, and clusters analysis. Megascopic observations showed the characteristics of tsunami deposits in Batu Hideung area with a thickness of 2-10 cm, tsunami and pra-tsunami deposits have sharp erosional contact, light brown to grayish brown, fine sand to gravel, moderately to very poorly sorted, consist of calcite, quartz, feldspar, pyroxene, pumice, corals, and mollusk shells. Grain size analysis, fine sand to gravel, moderately to poorly sorted, unimodal-bimodal dominated by bimodal distribution, fining landward. Foraminifera analysis, there are 14 species of benthonic foraminifera with intact and partially fragmented conditions, the environment of transition-middle neritic. There is a mixing of the origin tsunami deposits environment from the inner neritic zone with the middle neritic. Chemical element analysis shows that element content of Ca and Sr that are characteristic of the marine environment are relatively increased in tsunami deposits compared to pra-tsunami deposits, element content of Fe amd Ti is relatively decreased in tsunami deposits compared to pra-tsunami deposits. Cluster analysis shows there are one to three layers of tsunami deposits, indicate the number of tsunami waves occurence. The difference in the character of tsunami deposits due to a flank collapse and tsunami deposits due to earthquakes and storm deposits can be seen from the parameters of sorting and content of fauna Bentos that can indicate the origin environment of the sediment. Tsunami sediment caused by volcanic collapse and earthquake is medium-very bad sorted, while storm sediment is good sorted. The content of benthic fauna in tsunami deposits by volcanic collapse shows that the environment where tsunami deposits originate from the transition-middle neritic, in the tsunami deposits by the earthquake (2006 Pangandaran tsunami in the Karapyak area) originating from the transition-inner neritic.