Abstract
Abstract. Fogo in the Cabo Verde archipelago off western Africa is one of the most prominent and active ocean island volcanoes on Earth, posing an important hazard both to local populations and at a regional level. The last eruption took place between 23 November 2014 and 8 February 2015 in the Chã das Caldeiras area at an elevation close to 1800 ma.s.l. The eruptive episode gave origin to extensive lava flows that almost fully destroyed the settlements of Bangaeira, Portela and Ilhéu de Losna. During December 2016 a survey of the Chã das Caldeiras area was conducted using a fixed-wing unmanned aerial vehicle (UAV) and real-time kinematic (RTK) global navigation satellite system (GNSS), with the objective of improving the terrain models and visible imagery derived from satellite platforms, from metric to decimetric resolution and accuracy. The main result is a very high resolution and quality 3D point cloud with a root mean square error of 0.08 m in X, 0.11 m in Y and 0.12 m in Z, which fully covers the most recent lava flows. The survey comprises an area of 23.9 km2 and used 2909 calibrated images with an average ground sampling distance of 7.2 cm. The dense point cloud, digital surface models and orthomosaics with 25 and 10 cm resolutions, a 50 cm spaced elevation contour shapefile, and a 3D texture mesh, as well as the full aerial survey dataset are provided. The delineation of the 2014/15 lava flows covers an area of 4.53 km2, which is smaller but more accurate than the previous estimates from 4.8 to 4.97 km2. The difference in the calculated area, when compared to previously reported values, is due to a more detailed mapping of the flow geometry and to the exclusion of the areas corresponding to kīpukas (outcrops surrounded by lava flows). Our study provides a very high resolution dataset of the areas affected by Fogo's latest eruption and is a case study supporting the advantageous use of UAV aerial photography surveys in disaster-prone areas. This dataset provides accurate baseline data for future eruptions, allowing for different applications in Earth system sciences, such as hydrology, ecology and spatial modelling, as well as to planning. The dataset is available for download at https://doi.org/10.5281/zenodo.4718520 (Vieira et al., 2021).
Highlights
Detailed knowledge of volcanic eruptions and their products, evolution and impacts is of paramount importance for hazard assessment and for advancing our capability to forecast the likely behaviour of future eruptions
The full point cloud has an average of 15.9 points m−2 and a standard deviation of 6.5 points m−2 (Table 2), with most of the area showing values above 15 points m−2 (Fig. 10)
The 23.9 km2 very high resolution digital surface model and orthophoto mosaic of the Chã das Caldeiras lava fields developed from unmanned aerial vehicle (UAV) surveys of December 2016 show very high detail and accuracy, with a resolution of 25 cm and root mean square error (RMSE) of 10.3 cm
Summary
Detailed knowledge of volcanic eruptions and their products, evolution and impacts is of paramount importance for hazard assessment and for advancing our capability to forecast the likely behaviour of future eruptions. Very high resolution digital terrain datasets of recently erupted lava fields may be used to plan mitigation and reconstruction strategies They allow for very high resolution mapping of small-scale features, such as pressure ridges, fractures, lava types and kıpukas (i.e. small “islands” – interior elevations surrounded by lava) that contribute to process studies and to a better understanding of the eruption and post-eruption landscape dynamics. The usefulness of such datasets is greatly enhanced when these are freely available to governmental agencies, decision-making bodies and the scientific community alike
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