Lava flow hazard at Fogo Volcano, Cabo Verde, before and after the 2014–2015 eruption

Abstract

Abstract. Lava flow simulations help to better understand volcanic hazards and may assist emergency preparedness at active volcanoes. We demonstrate that at Fogo Volcano, Cabo Verde, such simulations can explain the 2014–2015 lava flow crisis and therefore provide a valuable base to better prepare for the next inevitable eruption. We conducted topographic mapping in the field and a satellite-based remote sensing analysis. We produced the first topographic model of the 2014–2015 lava flow from combined terrestrial laser scanner (TLS) and photogrammetric data. This high-resolution topographic information facilitates lava flow volume estimates of 43.7 ± 5.2 × 106 m3 from the vertical difference between pre- and posteruptive topographies. Both the pre-eruptive and updated digital elevation models (DEMs) serve as the fundamental input data for lava flow simulations using the well-established DOWNFLOW algorithm. Based on thousands of simulations, we assess the lava flow hazard before and after the 2014–2015 eruption. We find that, although the lava flow hazard has changed significantly, it remains high at the locations of two villages that were destroyed during this eruption. This result is of particular importance as villagers have already started to rebuild the settlements. We also analysed satellite radar imagery acquired by the German TerraSAR-X (TSX) satellite to map lava flow emplacement over time. We obtain the lava flow boundaries every 6 to 11 days during the eruption, which assists the interpretation and evaluation of the lava flow model performance. Our results highlight the fact that lava flow hazards change as a result of modifications of the local topography due to lava flow emplacement. This implies the need for up-to-date topographic information in order to assess lava flow hazards. We also emphasize that areas that were once overrun by lava flows are not necessarily safer, even if local lava flow thicknesses exceed the average lava flow thickness. Our observations will be important for the next eruption of Fogo Volcano and have implications for future lava flow crises and disaster response efforts at basaltic volcanoes elsewhere in the world.

Synergic Use of Multi-Sensor Satellite Data for Volcanic Hazards Monitoring: The Fogo (Cape Verde) 2014–2015 Effusive Eruption

“…The area coverage obtained by visual analysis of medium resolution imagery (L8 and EO-1) is estimated equal to 4.97 km 2 , in line with the results of EMS and by Cappello et al (2016). This value is very close to the one estimated with more sophisticated techniques that require more computational efforts or in situ measurements, such as differential DEM (Bagnardi et al, 2016), and Terrestrial Laser Scanner (TLS) combined with structure from motion data (Richter et al, 2016). Bagnardi et al (2016) and Richter et al (2016) estimate a lava coverage for this eruption of 4.8 and 4.85 km 2 , respectively, i.e., about 0.1 km 2 of difference with respect our results.…”

High-Resolution Digital Elevation Modeling from TLS and UAV Campaign Reveals Structural Complexity at the 2014/2015 Holuhraun Eruption Site, Iceland

“…Terrestrial Laser Scanning (TLS) is based on the principles of LiDAR (Light Detection and Ranging), which measures the time delay between emitted laser pulses and their echo receptions (Fornaciai et al, 2010;Richter et al, 2016). We used a Riegl VZ-6000 scanner ( Figure 2B), which features a rotating head scanner with a horizontal field of view of 360 • and a vertical field of view of −30 to 30 • .…”

“…Using the highly consistent TLS data with millions of possible GCPs for the registration of our SfM point clouds made the additional measurement of GCPs in the field redundant. Therefore, the procedure of referencing one point cloud against another reference point cloud is similar to that described in Richter et al (2016). This technique was beneficial, as placing GCPs on sharp fresh lava flow surfaces is difficult.…”

Topographic Changes During the 2018 Kīlauea Eruption From Single‐Pass Airborne InSAR

“…Changes in topography can be precisely estimated by differencing digital elevation models (DEMs) acquired before, during, and after an event (Stevens et al, ). The integration of topographic changes caused by the emplacement of lava flows or by the growth of domes can provide direct estimates of effused volumes (e.g., Bagnardi et al, ; Diefenbach et al, ; Favalli et al, ; Poland, ; Richter et al, ; Rowland et al, ), whereas measurements of topography loss caused by the formation of volcanic craters and calderas can be directly linked to volume loss in a subsurface magma reservoir (Gudmundsson et al, ).…”

“…Changes in topography can be precisely estimated by differencing digital elevation models (DEMs) acquired before, during, and after an event (Stevens et al, 1999). The integration of topographic changes caused by the emplacement of lava flows or by the growth of domes can provide direct estimates of effused volumes (e.g., Bagnardi et al, 2016;Diefenbach et al, 2013;Favalli et al, 2010;Poland, 2014;Richter et al, 2016;Rowland et al, 2003), whereas measurements of topography loss caused by the formation of volcanic craters and calderas can be directly linked to volume loss in a subsurface magma reservoir (Gudmundsson et al, 2016). Kīlauea Volcano, Hawai'i ( Figure 1), has been one of the most active volcanoes in the world since the onset of the long-lasting Pu'u 'Ō'ō eruption in 1983 and the most productive in terms of total volume of lava effused in recent years (>4 km 3 ; Poland, 2014).…”