## 7 Conclusions  
In this work, a new change detection methodology for object-based mapping of lava flows was developed using PlanetScope data. In addition, ash and tephra deposits could be detected using difference analysis of the Normalized Difference Vegetation Index (_dNDVI_). The developed change detection method combines the advantages of the very high resolution (VHR) PlanetScope data in an object-oriented approach. By combining the data with a drainage network model, Normalized Hotspot Indices (NHI) hotspot pixels (derived from Sentinel-2 and Landsat-8 data), and _dNDVI_ analyses, lava flows could be mapped even in unvegetated areas where volcanic deposits and the background have high spectral similarities. This is a major added value compared to methods described in the literature for detecting volcanic deposits (e.g., lava flows) using PlanetScope data based solely on _NDVI_ changes. The object-oriented change analysis obtained promising results, despite some generalizations in the modelling of potential lava areas. The PlanetScope data turned out to be highly useful in the analysis of volcanic hazards. Due to the high geometric resolution, even small-scale change processes can be detected. In addition, the high temporal resolution allows for the monitoring of highly dynamic processes in volcanic environments with high eruptive activity. This represents a significant advantage over comparable remote sensing systems that are commonly used for volcano monitoring. Due to the lack of bands in the shortwave or thermal infrared, no thermal information about volcanic activity can be collected with PlanetScope data. Using a multi-sensor analysis, e.g., combining PlanetScope with infrared data, these spectral limitations of PlanetScope can be circumvented. The data sources can thus complement each other and exploit the full potential of Earth observation in volcano monitoring. The results of this work and the aforementioned advantages of the data show that PlanetScope is very well suited for monitoring volcanic hazards and active volcanoes. The derived lava areas or ash and tephra deposits can serve as a basis or additional data for further work and thus support natural disaster management in the risk analysis of volcanic hazards. In addition, the developed methodology based on PlanetScope data can make an important contribution to rapid damage mapping in disaster areas in the future, e.g., in the context of the International Charter 'Space and Major Disasters'. Conceptualization, M.R. and S.P. ; methodology, M.R. ; validation, M.R. ; writing--original draft preparation, M.R. ; writing--review and editing, S.P. ; visualization, M.R. ; supervision, S.P. All authors have read and agreed to the published version of the manuscript. Financial support by the Client II Project Tsunami_Risk (BMBF Funding reference number 03G0906B) is acknowledged. The PlanetScope imagery used in this work was provided by Planet Labs through DLR's RESA program (RESA--RESA, BMWi grant 50 EE 1612). The datasets generated during the study are available from the corresponding author on reasonable request. The NHI hotspots were kindly provided by [PERSON] (University of Basilicata). No potential conflict of interest was reported by the authors. Appendix AFigure A2: (**a**) Potential lava areas based on distance to the outflow model (Copernicus DEM). All areas in the ”potential lava area” class are within 45 m of the nearest point to the extracted drainage flows. (**b**) Areas based on thermal overprinting (NHI area). This area was considered to be volcanically overprinted and thus is certainly covered with lava deposits. It forms the basis for modelling the lava flows in the areas with texture and brightness changes. Areas in the ”change area” class were classified using the GLCM and brightness thresholds and are within the ”potential lava area” class. Based on the NHI surface, region-growing modelling is performed into the ”change area”.