Satellite-based monitoring of active volcanoes provides crucial information about volcanic hazards and therefore is an essential component for the assessment of risk and disaster management. For this, optical imagery plays a critical role in the monitoring process. However, due to the spectral similarities of volcanic deposits and the surrounding background, the detection of lava flows and other volcanic hazards especially in unvegetated areas is a difficult task to manage with optical Earth observation data. In this study, we provide an object-oriented change detection method based on very high-resolution (VHR) PlanetScope imagery (3 m), short-wave infrared (SWIR) data from Sentinel-2 & Landsat-8 and digital elevation models (DEM) to map lava flows of selected eruption phases at tropical volcanoes in Indonesia (Karangetang 2018/2019, Krakatau 2018). Our approach can map lava flows in vegetated and in unvegetated areas. Procedures for mapping loss of vegetation (due to volcanic deposits) are combined with analysis of thermal anomalies derived from Sentinel-2/Landsat-8 SWIR imagery. Hydrological runoff modelling based on topographic data provides information about potential lava flow channels and areas. Then, within the potential lava flow area changes in texture and brightness between pre- and post-event PlanetScope imagery are analyzed to map the final lava flow area (also upstream in areas that have already been unvegetated prior to the lava flow event). The derived lava flow areas were qualitatively validated with multispectral false color time series from Sentinel-2 & Landsat-8. In addition, reports of the Global Volcanism Program (GVP) were analyzed for each eruption event and compared with the derived lava flow areas. The results show a high agreement of the derived lava flow areas with the visible thermal anomalies in the false color time series. Also, the analyzed GVP reports support the findings. Accordingly, the high geometric (3 m) and temporal resolution (daily coverage of the entire Earth’s landmass) of the PlanetScope constellation provides valuable information for the monitoring process of volcanic hazards. Especially the combination of the VHR PlanetScope imagery and the developed change detection methodology to map lava flow areas, provides a beneficially tool for the rapid damage mapping. In future, we plan to further automate this method in order to enable monitoring of active volcanoes in near-real-time.