Abstract
AbstractDetailed topographic data from volcanoes can yield key insights into the controls on volcanic activity as well as hazards. High‐resolution digital elevation models generated from remote sensing data enable comparison of the geomorphology and structure of large and inaccessible volcanoes. We present new topographic data for three peralkaline volcanoes in the Main Ethiopian Rift (Fentale, Corbetti, and Gedemsa) and one volcano in the Afar Rift (Dabbahu), combined with field observations, reveal previously unidentified post‐caldera deposits and craters. Vent and crater locations are aligned with rift‐parallel faults and also with rift‐cutting structures in a variety of orientations. Caldera shape is controlled by interaction with these structures. The relative frequency and type of eruption varies greatly between these volcanoes over the past 150 kyr. Gedemsa is now largely inactive; Fentale hosts deposits from many small volume eruptions (<0.1 km3); while Corbetti has produced several large eruptions (~0.4–0.5 km3). Morphometry of peralkaline rhyolite deposits at Corbetti and Fentale, including ogives and levees, provides constraints on rheology. Emplacement viscosities of ~108–1011 Pa s at Fentale are similar to or lower than calc‐alkaline rhyolites and consistent with experimental and theoretical studies. The observations presented here have significant implications for hazard assessment in the Ethiopian rift and highlight the importance of structural features in controlling the location, magnitude, and style of volcanic activity in the Main Ethiopian Rift.
Highlights
The geomorphology of volcanoes has long been used to investigate volcanic development and activity (Thouret, 1999)
No silicic peralkaline eruption has yet been observed, so the rheological constraints provided by morphology of peralkaline lava flow deposits are of significant interest and we further use our new data to assess the rheological properties of such flows
Satellite imagery and digital elevation models (DEMs) of Fentale, Gedemsa, and Corbetti enable an assessment of geomorphology and geological units, some of which have been mapped previously
Summary
The geomorphology of volcanoes has long been used to investigate volcanic development and activity (Thouret, 1999). We use high‐resolution digital elevation models (DEMs) to study the morphology of three volcanoes from the Main Ethiopian Rift (MER; Fentale, Gedemsa, and Corbetti) and one from Afar (Dabbahu, Figure 1). Using these data and complementary fieldwork, we (i) assess volcanic features, including observation of previously unidentified deposits; (ii) evaluate and compare caldera architecture; (iii) identify alignments of volcanic vents and craters; (iv) estimate eruptive volumes and frequencies along the rift; and (v) assess morphometry of peralkaline lava deposits. Volcanic activity in the MER has formed both silicic peralkaline “central” volcanoes and distributed mafic cones and lavas The poorly known volcanoes of the MER have become the focus of much recent work (Aspinall et al, 2011; Fontijn et al, 2018; Hutchison et al, 2015, Hutchison, Fusillo, et al, 2016, Hutchison, Biggs, et al, 2016, Hutchison, Pyle, et al, 2016, Hutchison et al, 2018; Lloyd, Biggs, Wilks, et al, 2018, Lloyd, Biggs, Birhanu, et al, 2018; Martin‐Jones et al, 2017; McNamara et al, 2018; Rapprich et al, 2016; Siegburg et al, 2017; Tadesse et al, 2018; Vye‐Brown et al, 2016)
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