Mud Volcanoes and Adjacent Vegetation Adaptation in the Rembang Zone, Indonesia: An Approach for Mud Volcano Investigation

Abstract

Abstract The Rembang Zone is a physiographic zone located in the northern part of Java, Indonesia. Rembang zone includes the areas from Rembang to Tuban and reaches the island of Madura. Ten mud volcanoes were identified, each with varying levels of eruptive intensity. Locals have reported that newly erupted mud materials can disrupt soil fertility in the surrounding areas, leading to vegetation death. Interestingly, we discovered several types of vegetation at mud volcano sites that have adapted, survived, and supported vegetation succession in the surrounding areas. Therefore, in this study, we investigated the vegetation around mud volcanoes in the Rembang Zone and its mud characteristics. We employed Sankey diagram analysis to explore the adapted plant taxa at mud volcano sites in the Rembang Zone. Additionally, we assessed the substrate using Scanning Electron Microscopy (SEM) and conducted geochemical analyses on fluid and non-condensable gas using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Gas Chromatography Mass Spectrometry (GC-MS). The results of this study reveal that there are at least 10 potential mud volcano sites in the Rembang Zone that could be inhabited by vegetation from the Poaceae family (20%), Asteraceae (18%), Cyperaceae (15%), Fabaceae (13%), Euphorbiaceae (9%), and other plant families (2%). These plants tend to adapt to the mud volcano substrate composed of Fe (0.00-0.35 mg/L), Ca (2.9-0.16%), Na (0.02-23.7%), and Cl (13-74%). This demonstrates that vegetation around mud volcanoes in the Rembang Zone can adapt to high-salinity conditions. SEM observations revealed a high smectite content associated with limestone rock. The mud volcanoes frequently emit gases such as N2 (2.3-73%), CH4 (0-8.8%), and CO2 (17-95%), indicating a tendency to produce substrates with nearly water-boiling temperatures (45-105°C). These findings serve as a reference for further understanding the presence of vegetation around mud volcanoes, particularly for identifying the presence of other mud volcanoes through remote sensing.