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

Abstract

Detailed 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.