STUDY OF THE 22ND DECEMBER 2018’S TSUNAMI DEPOSITS CHARACTERISTICS IN KALIANDA REGION, LAMPUNG

• Main Author: 'Ulya Insani, Mahabbatul
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/64611
• Institution: Institut Teknologi Bandung

On the 22nd December, 2018 volcanic activities of Anak Krakatau had generated an underwater landslide and triggered a tsunami around the Sunda Strait. The tsunami waves caused the formation of tsunami deposits along the coast of the Kalianda area, Lampung. This study was conducted to determine the characteristics of tsunami caused by volcanic collapse based on outcrop observations, macroscopic analysis of tsunami sediment samples, granulometric analysis, and microfaunal analysis of foraminifera. The samples in this study were taken from 4 locations around the Kalianda area, Perak Beach, Clara Cukuh Suak Beach, Banding Beach, and Wartawan Beach. Characteristics of tsunami deposits based on outcrop observations showed that tsunami deposits in the Kalianda area are 3-9 cm thick, light color, and erosional contact with the underlying paleosol layer. Megascopic observations of the tsunami sediments showed the characteristics of tsunami deposits in the form of light brown–light gray sand, very fine sand– medium sand with gravel–pebble-sized fragments, angular-rounded, poorly sorted, consisting of quartz, feldspar, pyroxene, calcite, and coral fragments. Granulometric analysis showed that the tsunami deposits had a bimodal grain size distribution curve. Based on the content of foraminifera, analysis of the depositional environment of the tsunami deposits indicated a mixture of inner neritic and middle neritic sediments. The character of the 2018 Kalianda tsunami deposits, which is a tsunami deposits due to the volcanic collapse, is compared with the character of the tsunami deposits caused by an earthquake. The characteristics of the tsunami deposits due to the earthquake compared are the 2004 Aceh tsunami deposits and the 2006 Pangandaran tsunami deposit. The 2018 Kalianda tsunami deposits shows relatively the same characteristics as the 2004 Aceh and the 2006 Pangandaran tsunami deposits, which are poorly sorted, very fine sand–very coarse sand. Benthic foraminifera analysis of the tsunami deposits due to the volcanic collapse shows that the environment from which the tsunami deposits originate is from inner neritic–middle neritic, while tsunami deposits due to the earthquakes are from the neritic to bathyal zones