A new reading using modern techniques of unpublished magnetic data acquired in Africa half a century ago has allowed us to strengthen our knowledge of the junction area between the Arabian, Somali and Nubian plates and to re-examine their tectonic evolution.
The use of modern techniques for the processing of a vast archive of Unpublished aeromagnetic data collected in the Afar region of Africa between 1968 and 1969 and integrated with more recent data from the Red Sea, Gulf of Aden and Yemen has allowed us to reconstruct in detail the crustal structure of the area and to re-examine itsevolution from a new perspective, enriching and strengthening knowledge on large rift systems.
The study, entitled “A review of the 1968 Afar Magnetic Survey data and integration with vintage Red Sea and Gulf of Aden data”, was recently published in the journal Journal of African Earth Science and involved a team of researchers from theNational Institute of Geophysics and Volcanology (INGV),Keele University, England and Australian P&R Geological Consultants.
“Africa is slowly splitting in two, with a major rift that runs across the entire continent and has its roots in the Afar region of northern Ethiopia.”, explains Richard De Ritis, researcher at INGV and co-author of the article. “It is a unique place in the world where three major rift systems converge—the Red Sea, the Gulf of Aden, and the East African Rift—forming one of the most geologically active and complex areas on the planet.”.
In this region, the processes that thin and break the continental crust are directly observable on the surface, transforming the Afar into a true natural laboratory for the study of crustal dynamics.
Thanks to the recovery, digitization and analysis of a vast archive of aeromagnetic data collected half a century ago in the Afar region and never used before, the authors of the study were able to confirm that The breaking of the Earth's crust began with the separation between Africa and Arabia along the Red Sea/Afar and Gulf of Aden areas., while the Main Ethiopian Rift (MER) reached the Afar region only at a relatively late stage in its tectonic history.
“With a coherent reading of the magnetic signal, integrated with more recent datasets from the Red Sea and the Gulf of Aden, we were able to strengthen a framework already proposed in the past.”, goes on Of Ritis. The analysis of magnetic anomalies reveals a crucial aspect for understanding the tectonics of the Afar. In the southern sector of the region, the WSW-ENE imprint of the Gulf of Aden trend is very clearly evident, while no magnetic trace appears of the younger Main Ethiopian Rift (MER), which is oriented NNE-SSW and known to be the northern branch of the great East African Rift. Proceeding north, the situation changes: in the northern Afar, the magnetic anomalies orient themselves along the NW-SE direction of the Red Sea, while further south, they align almost perfectly along the Gulf of Aden trend. This dual arrangement highlights the main geological fractures that drove the initial separation between Africa and Arabia..
According to the researchers, this distinctive magnetic alignment indicates that continental rifting initially developed along deep-seated fractures aligned with the Gulf of Aden and the Red Sea. The Ethiopian Rift was activated only later, likely fueled by the upwelling of a mantle superplume beneath East Africa, a process that is still ongoing.
The Afar represents an extraordinary example of how the continental crust can deform, thin and break under the combined effect of deep magmatism and tectonic thrusts.Over very long geological timescales, these processes could lead to the opening of a new ocean and the division of Africa into two distinct landmasses.
“Beyond their scientific significance, our findings highlight the importance of preserving and reevaluating past data, as interpretive models may change over time, but well-acquired data last forever.”he concludes Of Ritis.
Useful links:
National Institute of Geophysics and Volcanology (INGV)
Figure 1: Topographic map of Ethiopia showing the Afar Depression, the northern part of the rift system that crosses the African continent. Derived from the SRTM 1-ArcSecond DEM (about 30 m) from NASA's Jet Propulsion Laboratory.
Figure 2: Tectonic African Arabian Rift System: USGS / redrawn for Wikimedia Commons Public Domain (US Government work / USGS).
Figure 3: Geological map overlaid on the composite aeromagnetic map of Afar, Red Sea, Goa and Yemen.
Figure 4: 3D interpretive block of the African superplume beneath the Main Ethiopian Rift and the Afar region in the background.