East African rifting, volcanism and the African Superplume: An analogue for the Martian Valles Marineris and Tharsis Province

Category Tectonic & Seismotectonic
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Modisi, Motsoptse; Laletsang, Kebabonye
Holding Date 07 October 2008

The East African Rift System (EARS), an approximately 4,000 km long fracture system, may be preceding future continental breakup. It is one of the structures that characterizes the elevated terrains of East and Southern Africa and the southeast Atlantic Ocean collectively referred to as the African Superswell. This large bulge is regarded to be caused by uplift resulting from an upwelling mantle plume impinging on the base of the African Plate lithosphere. The fracture system is accompanied by volcanism that is restricted to the intra-tropical regions. This setting is analogous to that of the Valles Marineris (VM) and Tharsis Province of Mars, where the foregoing characteristics are broadly similar in terms of scale and mode of occurrence. The EARS, however, is longitudinally oriented while the VM is latitudinal. The greater effects of erosion and sedimentation on Earth caused by the sustained action of water probably account for the subdued relief as compared to that of Mars. We propose that the structural similarities may be linked to a common tectonic mechanism driven by an upwelling mantle plume. Plate tectonics is no longer active on Mars, and evidence from the analysis of the Martian magnetic data indicates that it was possibly active in the geological past. The African Superplume probably has a history traceable to the Mesozoic Era and is a likely tectonic driving force that contributed to the break up of Pangea and continues to be active up to now. The inner terrestrial Solar System comprises four planets with two having similar rotational mechanics, i.e. Earth and Mars. Each of these planets rotates about once every 24 hours (~24.6 hours in the case of Mars) with axes inclined to the sidereal orbit plane. Mercury and Venus rotate about once in each of their respective years (retrograde in the case of Venus). A buoyant and upwelling mantle plume originating in the lower mantle beneath the African Plate may have been influenced by the centrifugal force generated by the Earth’s rotation through geological time, thus concentrating surface swelling, fracturing and volcanism within the inter-tropical zone. An analogous mechanism is perceived for Mars as well, where the location of similar structures is probably influenced by axially symmetric mechanics. Lunar and Solar tidal effects may have also contributed to the concentration of major global-scale plumes and associated magmatism in the inter-tropical regions of Earth and Mars.