Morphological comparison of distributed volcanic fields in the main Ethiopian rift using high-resolution digital elevation models

Distributed volcanic fields of scoria cones, maars, tuff cones and lava flows represent a crucial expression of the interplay between magmatism, tectonics and surface processes in continental rifts. We compare the cone morphology of two fields (Butajira and East Ziway) in the Main Ethiopian Rift (MER), using high-resolution digital elevation models (DEMs) to investigate volumes, surface environment and age of emplacement. Volumes of individual cones are similar in both fields (mean ~4 × 106 m3) and lower than in other distributed volcanic fields located in extensional environments. Volcanism at Butajira has created linear clusters of superimposed cones, suggesting a small number of larger (107–108 m3) fissure eruptions compared to the isolated events at East Ziway. The presence of maars and deep craters within cones at Butajira indicates phreatomagmatic activity, not seen at East Ziway where cones may have been emplaced during a dry climate phase. Shape parameters, including curvature of cone rims and ratios of cone height, width and crater depth, suggest younger eruption ages at Butajira compared to East Ziway and the possibility of ongoing activity in this area. A broader survey of cone fields across the MER using the ASTER global digital elevation model fails to identify systematic variation in height, width and volume from cone morphology, limited by low-resolution. High-resolution topography provides a useful insight into rift environments at the time of emplacement, and further surveys across the Main Ethiopian Rift may advance our understanding of distributed volcanism in extensional settings and the hazards they present.