A pulse of mid-Pleistocene rift volcanism in Ethiopia at the dawn of modern humans

Abstract

The Ethiopian Rift Valley hosts the longest record of human co-existence with volcanoes on Earth, however, current understanding of the magnitude and timing of large explosive eruptions in this region is poor. Detailed records of volcanism are essential for interpreting the palaeoenvironments occupied by our hominin ancestors; and also for evaluating the volcanic hazards posed to the 10 million people currently living within this active rift zone. Here we use new geochronological evidence to suggest that a 200 km-long segment of rift experienced a major pulse of explosive volcanic activity between 320 and 170 ka. During this period, at least four distinct volcanic centres underwent large-volume (>10 km3) caldera-forming eruptions, and eruptive fluxes were elevated five times above the average eruption rate for the past 700 ka. We propose that such pulses of episodic silicic volcanism would have drastically remodelled landscapes and ecosystems occupied by early hominin populations.

Using Lake Sediment Cores to Improve Records of Volcanism at Aluto Volcano in the Main Ethiopian Rift

“…In general, the microlite-rich glass has the same major element composition as the microlite-poor glass. Microlites in other settings have been found to grow in systems ≤4-km depth (e.g., Cashman & McConnell, 2005;Hammer et al, 1999), we infer that this was likely the case at Aluto where ã 4-km deep magma storage is observed (Hutchison, Fusillo, et al, 2016). This trace element difference can be explained by degassinginduced crystallization of a eutectic melt and associated enrichment of the relevant incompatible elements (such as Ba; e.g., Scaillet & MacDonald, 2001).…”

“…We believe Aluto to be one of the most frequently active volcanoes in the region (Fontijn et al, 2018;Hutchison, Fusillo, et al, 2016;, and so developing understanding of eruption size and frequency is key to improving hazard assessment. We believe Aluto to be one of the most frequently active volcanoes in the region (Fontijn et al, 2018;Hutchison, Fusillo, et al, 2016;, and so developing understanding of eruption size and frequency is key to improving hazard assessment.…”

The Geomorphology, Structure, and Lava Flow Dynamics of Peralkaline Rift Volcanoes From High‐Resolution Digital Elevation Models

“…Volcanic activity in the MER has formed both silicic peralkaline “central” volcanoes and distributed mafic cones and lavas (e.g., B. Abebe et al, ; Gibson, ). The poorly known volcanoes of the MER have become the focus of much recent work (Aspinall et al, ; Fontijn et al, ; Hutchison et al, , Hutchison, Fusillo, et al, , Hutchison, Biggs, et al, , Hutchison, Pyle, et al, , Hutchison et al, ; Lloyd, Biggs, Wilks, et al, , Lloyd, Biggs, Birhanu, et al, ; Martin‐Jones et al, ; McNamara et al, ; Rapprich et al, ; Siegburg et al, ; Tadesse et al, ; Vye‐Brown et al, ).…”

“…The silicic MER volcanoes are in a post‐caldera stage of evolution (Hutchison, Fusillo, et al, ). Four volcanoes have shown recent geodetic unrest (Aluto, Corbetti, Bora and Haledebi), with some deformation associated with ongoing geothermal activity (Biggs et al, ; Hutchison et al, , Hutchison, Biggs, et al, ; Lloyd, Biggs, Wilks, et al, , Lloyd, Biggs, Birhanu, et al, ).…”

“…Corbetti and Aluto are considered the most active volcanic centers in the rift, with deposits from explosive eruptions implying an eruptive flux of 0.01–0.1 km 3 (magma)/kyr over the past 12 kyr (Fontijn et al, ). This flux has declined significantly since the mid‐Pleistocene peak of caldera‐forming activity, when eruptive rates at Aluto and Corbetti may have been as high as 0.5–0.75 km 3 /kyr (Hutchison, Fusillo, et al, ).…”