The spatial distribution and evolution of volcanic vents in monogenetic fields in active extensional tectonic setting: Examples from the northern Main Ethiopian Rift (Ethiopia)

Monogenetic volcanic fields are present in different geo-tectonic settings (subduction, divergence and intraplate
settings) consisting of tens to hundreds of volcanic constructs (cones, maars, fissures, small shields) that are the
physical expression of distributed volcanism.
Notably, the spatial distribution of the volcanic constructs in volcanic fields often shows a spatial clustering
that is thought to be linked to shallow (i.e., crustal strain, structural inheritance) and deep processes (i.e., magma
input, composition and rheology). Noteworthy, the spatial distribution of vents (cones, maars, fissures, small
shields) is the final frame of the history of the volcanic field and does not provide information about its timeevolution.
Consequently, when a vent spatial clustering is assessed for a particular volcanic field two questions remain
unanswered: i) have the vents always been clustered during the life of the volcanic field? ii) If not, when did the
clustering of vents begin? To answer these questions, the spatial distributions of vents along with their
morphologic classification have been applied to volcanic fields located in an active tectonic and volcanic area.
The northern Main Ethiopian Rift, being its geo-tectonic setting and its geologic evolution well known, is the
locale where the time evolution of vent spatial clustering can be investigated. Spatial distribution and
morphometric analysis of vents have been applied to three well known monogenetic volcanic fields (Debre Zeyt,
Wonji and Kone) in the northern Main Ethiopian Rift. Vent clustering initiated when about 60% of the vents
formed within each of the above mentioned fields. The Kone volcanic field show vent clustering since the
beginning suggesting that, within a specific tectonic setting, vent clustering is favoured by crustal strain partitioning
and associated volcanic activity.