STUDY OF SURFACE TEMPERATURE AND GEOMORPHOLOGY IN THE TIRIS GEOTHERMAL AREA, LAMONGAN VOLCANIC SYSTEM, EAST JAVA, INDONESIA

Abstract

This research applied the remote sensing method to map the land surface temperature (LST) distribution and geomorphology of the Tiris geothermal area (TGA), situated within the broader Lamongan Volcano Complex. The investigation covered a 73 km² area, encompassing both the TGA and the Lamongan Volcanic Field (LVF). The distribution of LST was ascertained by processing thermal infrared images acquired by the Landsat-8 satellite. Geomorphological characterization of the study area was achieved through the analysis of 567-band composite multispectral Landsat-8 imagery in conjunction with Digital Elevation Model (DEM) data from the Shuttle Radar Topography Mission (SRTM). The geomorphological conditions were depicted through visual delineation applied to the 567-band composite map and a three-dimensional topographical model. The study’s findings indicate that the LST across the area ranges from 15.84°C to 41.05°C. It was observed that the thermal hotspots within the study area were predominantly located in built-up areas and regions of bare land, rather than being directly correlated with known geothermal surface manifestations. No significant high-LST anomaly was detected in the immediate vicinity of the TGA hot springs. This is likely due to the confounding influence of the Tancak River, where the thermal signature of the hot springs is mixed with the ambient temperature of the river's water flow. The geomorphological investigation clarified the structural framework of the Lamongan Volcano, identifying two principal lineaments with northwest-southeast and northwest-east orientations. Furthermore, a distinct fault was identified within the TGA, trending northwest-southeast and spatially associated with the Tancak watershed, suggesting a structural control on the location of surface manifestations.