Mapping Recent Lava Flows at Mount Etna Using Multispectral Sentinel-2 Images and Machine Learning Techniques

Abstract

Accurate mapping of recent lava flows can provide significant insight into the development of flow fields that may aid in predicting future flow behavior. The task is challenging, due to both intrinsic properties of the phenomenon (e.g., lava flow resurfacing processes) and technical issues (e.g., the difficulty to survey a spatially extended lava flow with either aerial or ground instruments while avoiding hazardous locations). The huge amount of moderate to high resolution multispectral satellite data currently provides new opportunities for monitoring of extreme thermal events, such as eruptive phenomena. While retrieving boundaries of an active lava flow is relatively straightforward, problems arise when discriminating a recently cooled lava flow from older lava flow fields. Here, we present a new supervised classifier based on machine learning techniques to discriminate recent lava imaged in the MultiSpectral Imager (MSI) onboard Sentinel-2 satellite. Automated classification evaluates each pixel in a scene and then groups the pixels with similar values (e.g., digital number, reflectance, radiance) into a specified number of classes. Bands at the spatial resolution of 10 m (bands 2, 3, 4, 8) are used as input to the classifier. The training phase is performed on a small number of pixels manually labeled as covered by fresh lava, while the testing characterizes the entire lava flow field. Compared with ground-based measurements and actual lava flows of Mount Etna emplaced in 2017 and 2018, our automatic procedure provides excellent results in terms of accuracy, precision, and sensitivity.

The VEI 2 Christmas 2018 Etna Eruption: A Small But Intense Eruptive Event or the Starting Phase of a Larger One?

“…Lava flow output from the lower part of the eruptive fissure toward the VdB continued for a few more days until the early morning of 27 December. The lava flow field reached a total extension of 0.88 km 2 [42]. Overall, the eruptive fissure was about 2300 m long, and reached the minimum altitude of 2400 m a.s.l., propagating with a speed of~0.7 m/s, which was the highest recorded at Etna in the last 110 years [41].…”

“…Lava flow output from the lower part of the eruptive fissure toward the VdB continued for a few more days until the early morning of 27 December. The lava flow field reached a total extension of 0.88 km 2 [42].…”

Overflows and Pyroclastic Density Currents in March-April 2020 at Stromboli Volcano Detected by Remote Sensing and Seismic Monitoring Data

“…Recently, the high spatial resolution and freely available information coming from the Multispectral Imager (MSI) on-board Sentinel-2 satellite has been used to facilitate the two-dimensional (2D) mapping of lava flows [71] through a new Machine Learning (ML) classifier, which discriminates the recent lava flows from pre-and post-eruptive multispectral images acquired by MSI, combined with pre-eruptive digital topography. Bands 2, 3, 4, and 8 at the spatial resolution of 10 m are used as input to the classifier.…”

Volcanic Hot-Spot Detection Using SENTINEL-2: A Comparison with MODIS–MIROVA Thermal Data Series

“…Nevertheless, because of their recent availability, the SENTINEL-2 (hereafter S2) thermal dataset is partially still under-investigated in volcanological studies: a few works started to use these images, mainly for studying qualitatively a specific eruption or volcanic phase [37][38][39], mapping lava flows [40] or as a comparison dataset to calculate pixel-integrated temperatures or to infer thermal model of a specific volcanic phenomena [41,42].…”