Geomorphological mapping and landform characterization of Semeru volcano after the eruption in 2021

Abstract

The eruption of the Semeru volcano in 2021 has diverse impacts on the landscape and surroundings. It is essential to detect recent landscape features to promptly evacuate personnel and property near the volcano and take emergency treatment measures in case of sudden danger. This study presents a detailed geomorphological map on a 1:50.000 scale for the Semeru volcano after the eruption in 2021. The analysis of the hybrid approach and the on-screen image interpretation (OSII) method on DEM data, optical satellites, and lithology units was carried out to obtain morphological, morphochronological, and morphoarrangement information. While, morphoprocess information was obtained through field observations. We used DAS Rejali for our study area. The results of identifying geomorphological conditions divide the Rejali watershed area into 32 landforms consisting of landform units from volcanic, structural, fluvial, and marine processes. Twenty-three land units in the research location are landforms from volcanic processes. This condition causes morphological conditions, material availability, and processes that dominantly reflect the characteristics of an active volcano. In addition, the landform units from the fluvial process in the Rejali watershed area were identified as many as six units in the form of floodplains of lahar flows along the main river. Landforms with structural genesis were placed in Mandalika formation and diorite rock breakthrough. The structural formation in the Rejali watershed has retention and rock structures that are not easily eroded by water. It becomes a bottleneck formation as a barrier between the upstream and middle areas