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Abstract:
Bioko Island (Equatorial Guinea) consists of three coalescing Quaternary shield volcanoes where lava flows are the primary volcanic hazard. The last documented effusive eruption on the island occurred at Pico Basilé in 1923, and the opening of steam vents in 2012 at the summit demonstrates the volcanic system remains active. However, lava flow hazards on Bioko have not previously been studied, and thus need to be assessed. The dense vegetation makes much of the island difficult to access. Hence, we use synthetic aperture radar data from the TerraSAR-X and TanDEM-X satellite instruments, completed with field work.We mapped 437 vents among which 342 scoria cones were well defined. The vents are clustering along the main NE-SW-trending rift at Pico Basilé, and between Pico Biaó and Gran Caldera de Luba. This data set is used to build a probability density function of future vent opening. Additionally, we were able to map six lava flows from source to front, ranging in length from 1.9-2.7 km at Pico Basilé, and 2.3-4.0 km at the two southern volcanoes. This data will serve as input to deliver a probabilistic estimation of the lava flow inundation area, through Q-LavHa lava simulation. Furthermore, we collected 22 samples from 12 lava flows during a fieldwork campaign in 2022. The samples reveal an alkaline-basaltic composition with some variable bubble and crystal content. Based on rheological parameters derived from the samples and flow geometries, we will use the deterministic FLOWGO model to refine our understanding of lava flows on Bioko.
