DOI: 10.5281/zenodo.17348855
title: Data set: Hydrothermal weakening and slope instability at Vulcano (Italy) analyzed using drones and in-situ strength measurements

description: This is the complementary data set supporting "Hydrothermal weakening and slope instability at Vulcano (Italy) analyzed using drones and in-situ strength measurements" (DOI: 10.1038/s43247-025-03014-5)

Summary description: 

This dataset originates from a study conducted at La Fossa cone on Vulcano Island (Italy), the southernmost active center of the Aeolian volcanic archipelago. La Fossa serves as an outstanding natural laboratory for studying volcanic instability, due to its well-documented history of mass wasting, extensive hydrothermal alteration, and persistent fumarolic activity. These processes collectively modify rock properties, influence slope stability, and contribute to volcanic hazard potential.

To investigate the mechanical and spectral signatures of hydrothermal alteration, we employed an integrated approach combining high-resolution drone-based remote sensing, spectral analysis, and in situ mechanical testing. Drone imagery was obtained in 2019, during an ideal period of fumoral and weather conditions, creating a data set favorable for investigating spectral surface conditions. Data were reprocessed in Agisoft Metashape (Version 1.5.2.7838) to generate detailed orthomosaics and digital surface models (DSMs), providing a high-resolution spatial framework for subsequent image classification. Using principal component analysis (PCA) and both supervised and unsupervised classification techniques, we identified and mapped zones of hydrothermal alteration with differing intensities and mineralogical expressions. These spectral results were validated and interpreted in the context of field observations.

Field-based measurements of rock strength were obtained using a Schmidt hammer, allowing us to estimate uniaxial compressive strength (UCS) across altered and unaltered zones.

Our combined analysis reveals:





A heterogeneous distribution of hydrothermal alteration types and intensities.




A clear alteration to the strength relationship, where rock strength decreases as alteration intensity increases.




A clear association between alteration zones and deep erosional or landslide scars.



Overall, this integrated dataset demonstrates how hydrothermal alteration weakens volcanic edifices and promotes structural instability. The combination of drone-based imaging, spectral classification, and field-based strength testing provides a robust framework for evaluating rock weakening, slope failure mechanisms, and hazard assessment at active volcanoes.

Data provided: 

Here we provide a high-resolution orthomosaic, DSM, composite PCA, and associated single components (PC1, PC2, and PC3), as well as a shapefile containing all locations of the Schmidt hammer measurements with values in the attributes table. In addition, a table containing all GPS coordinates and Schmidt-Hammer values is provided. 

File description: 



vulcano_orthomosaic_2019.tif is the orthomosaic created in Agisoft Metashape (Version 1.5.2.7838) from a drone survey conducted at 150 m in a grid-like pattern using a DJI Phantom 4 UAV equipped with a 20 megapixel camera. 

Lafossa_vulcano_dem_2019.tif is the DEM processed in Agisoft Metashape (Version 1.5.2.7838) from the same drone survey described above.

Lafossa_vulcano_PC1_2019.tif is the single principal component 1 produced in ArcGIS Pro (v3.3.0) and containing approximately 95.6% of the variance within the analysis. 

Lafossa_vulcano_PC2_2019.tif  is the single principal component 2 produced in ArcGIS Pro (v3.3.0) and containing approximately 2.7% of the variance within the analysis.  

Lafossa_vulcano_PC3_2019.tif is the single principal component 3 produced in ArcGIS Pro (v3.3.0) and containing approximately 1.6% of the variance within the analysis. 

Lafossa_vulcano_PCAcomposite_2019.tif is the color composite of PC1, PC2, and PC3 produced in ArcGIS Pro (v3.3.0), which was used to highlight the areas reflecting surfaces containing hydrothermal alteration. 

SchmidtHammer_Locations_and_Values.shp is the shape file produced in ArcGIS Pro (v3.3.0), which contains all of the locations of the Schmidt Hammer measurements. In addition, the embedded attribute table has the corresponding relative strength (Schmidt Hammer) measurement. 

SchmidtHammer_measurments_withGPS.pdf is the table of all Schmidt hammer coordinates and associated R-Values. 
description: Processing steps: 



Import all files into a GIS software. 



vulcano_orthomosaic_2019.tif

Lafossa_vulcano_dem_2019.tif

Lafossa_vulcano_PC1_2019.tif

Lafossa_vulcano_PC2_2019.tif

Lafossa_vulcano_PC3_2019.tif

Lafossa_vulcano_PCAcomposite_2019.tif

SchmidtHammer_Locations_and_Values.shp



 Using the Lafossa_vulcano_PCAcomposite_2019.tif create a supervised classification with training areas inside the red to pink regions of the PCA as Altered, and another training area outside of the red to pink regions (Blue and Green) as unaltered. 

The region classified as altered creates a mask towards your high-resolution orthomosaic (vulcano_orthomosaic_2019.tif) and creates a supervised classification. Here we created four classes. This will create your classification map of alteration intensity. 

 With your Schmidt hammer points layer (SchmidtHammer_Locations_and_Values.shp) overlaid on top of the produced classification map, you can now extract Schmidt points associated with different classifications, allowing for analysis. 


In case of further questions, please contact bdejarna@gfz.de