Identification and characterization of eruption sites and lava flows within the Manda-Hararo rift segment, Afar Depression, Ethiopia

An integrated geological mapping approach involving remote sensing, three-dimensional image analysis, and limited fieldwork for ground-proofing has been employed in the extensive volcanic region of the Afar Depression in Ethiopia. This approach has enabled identification of the spatial and temporal relationship between continental rift axis fissure-fed volcanism and central volcanoes, through the identification of lava flows at the scale of single eruptive units and the temporal development of faults associated with continental rifting. Analysis of topography and surface rock chemistry based false colour Landsat, ASTER, hyperspectral and LiDAR imagery is conducted within an immersive three-dimensional visualisation suite using SocetSet and Geovisionary software and subsequently ground-proofed by the targeted field studies. Through this high-resolution mapping technique we establish the eruption history of the area at the scale of individual eruption units, identifying basaltic fissure vents, cinder cones, the character, volumes and extent of individual lava flows. The relationship between lavas from discrete volcanic complexes and rift axial fissure-fed flows are illustrated for the Dabbahu volcano and the Manda-Hararo rift segment. Results show a spread of eruption sites and vent character about the axis of the rift segment, similar to recent models of mid-ocean ridge volcanism (e.g. Maclennan, 2010), rather than repetitive eruptions from central fissure vents. Identification of individual eruption units also facilitates reconstruction of fault scarp development and propagation based on the distribution, morphology and emplacement style of different basaltic flow fields. High-resolution mapping is an important tool for interpretation of the timing and relationships of rifting and volcanism in the East African Rift.