Mount Fentale

Fentale is a volcanic complex at the N end of the Main Ethiopian Rift that includes a main stratovolcano and caldera with various subsidiary features. Products are primarily rhyolitic obsidian lava flows with minor tuffs. Welded pantelleritic ash flows accompanied formation of a 2.5 x 4.5 km elliptical summit caldera, with steep-sided walls, that trends WNW-ESE, perpendicular to the rift. Post-caldera vents lie along the same orientation. Lava flows that appear to be more recent are present on the NE and SW flanks, and dark trachytic and obsidian lava flows occur on the caldera floor. Sometime during about 1770-1808 CE basaltic lava flows effused from a 3.5-km-long fissure on the S flank; there were also lava flows in the caldera. During 2015 there was a seismic swarm and deformation NE of Fentale, caused by a dike intrusion that Temtime et al. (2020) determined was about 6 km long (striking N29°E) and 2 m wide, with a depth range of 5.4-8 km below the surface (volume change of about 33 x 106 m3).