Pulses of deformation reveal frequently recurring shallow magmatic activity beneath the Main Ethiopian Rift

Abstract

[1] Magmatism strongly influences continental rift development, yet the mechanism, distribution, and timescales on which melt is emplaced and erupted through the shallow crust are not well characterized. The Main Ethiopian Rift (MER) has experienced significant volcanism, and the mantle beneath is characterized by high temperatures and partial melt. Despite its magma-rich geological record, only one eruption has been historically recorded, and no dedicated monitoring networks exist. Consequently, the present-day magmatic processes in the region remain poorly documented, and the associated hazards are neglected. We use satellitebased interferometric synthetic aperture radar observations to demonstrate that significant deformation has occurring at four volcanic edifices in the MER (Alutu, Corbetti, Bora, and Haledebi) from 1993 to 2010. This raises the number of volcanoes known to be deforming in East Africa beyond 12, comparable to many subduction arcs despite the smaller number of recorded eruptions. The largest displacements are at Alutu volcano, the site of a geothermal plant, which showed two pulses of rapid inflation (10-15 cm) in 2004 and 2008 separated by gradual subsidence. Our observations indicate a shallow (<10 km), frequently replenished zone of magma storage associated with volcanic edifices and add to the growing body of observations that indicate shallow magmatic processes operating on a decadal timescale are ubiquitous throughout the East African Rift. In the absence of detailed historical records of volcanic activity, satellitebased observations of monitoring parameters, such as deformation, could play an important role in assessing volcanic hazard.

Spatial relationship between earthquakes and volcanic vents in the central-northern Main Ethiopian Rift

“…These intrusions combined with faulting and fracturing of the crust, likely accommodated most of the extension (Keir et al, 2006(Keir et al, , 2011a. High conductivities observed at both~2-km and~15-km-depth in a magnetotelluric survey across Boset volcano (Whaler and Hautot, 2006;Keir et al, 2009), combined with b10-km-deep magma bodies beneath Corbetti, Aluto, Bora, Haledebi and Ayelu-Amoissa volcanoes modelled from InSAR data (Biggs et al, 2011;Keir et al, 2011b), suggests persistence of meltrich zones in both mid-and upper crust beneath many QuaternaryRecent volcanic centres.…”

Historical Volcanism and the State of Stress in the East African Rift System

“…Gudmundsson (2012) suggests that over the long-term reservoirs with irregular boundaries are thermally and mechanically unstable and will tend to evolve to smoother equilibrium geometries. Most InSAR images of deforming volcanoes, particularly in East Africa show a simple bulls-eye pattern of motion (e.g., Biggs et al, 2009Biggs et al, , 2011, equivalent to the deformation produced by a point-or a spherical/ellipsoidalpressure source, in an isotropic half space, typically attributed to varying pressure within a magma reservoir ( Figure 2E) and originally analyzed as a either a pressurized point (Anderson, 1936;Mogi, 1958) or pressurized cavity (Savin, 1961). While deformation is an indicator of an active magmatic system and can be shown to have a statistical link to the likelihood of eruption (Biggs et al, 2014), the mechanisms that produce deformation are varied, and implications for the stress field are poorly understood.…”

The development of extension and magmatism in the Red Sea rift of Afar

“…1 and 2). These encapsulate active volcanoes (Biggs et al, 2011), aligned monogenetic cones (e.g., Ebinger and Casey, 2001;Mazzarini, 2008;Williams et al, 2004), and small-offset faults striking perpendicular to the direction of extension (Fig. 2) (e.g., Agostini et al, 2011a,b;Corti, 2008Corti, , 2009Hayward and Ebinger, 1996;Keir et al, 2011a).…”