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 even darker trachytic and obsidian lava flows occur on the caldera floor. An eruption during the 13th century destroyed an Abyssinian town and church to the south. In 1820 CE basaltic lava flows effused from a 4-km-long fissure on the S flank; lava also flowed onto the caldera floor. 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).