The East African Rift System is slowly breaking down, with Madagascar breaking apart

The African continent is slowly separating into several large and small tectonic blocks along the divergent East African rift system, continuing towards Madagascar, the long island just off the coast of Southeast Africa, which in turn will separate into smaller islands.

These developments will redefine Africa and the Indian Ocean. The discovery comes in a new study by D. Sarah Stamps of the Department of Geosciences for the journal Geology. The rupture is a continuation of the destruction of the supercontinent Pangea some 200 million years ago.

Rest assured, though, this won’t happen anytime soon.

“The disintegration rate today is millimeters per year, so it will take millions of years for new oceans to start forming,” said Stamps, assistant professor at Virginia Tech College of Science. “The rate of extension is faster in the north, so we’ll see the new oceans forming there first.”

In this 2016 photograph, geoscience graduate student Tahiry Rajaonarison installed a GPS tool in northern Madagascar. Behind Tahir is the Indian Ocean and a rocky island. Photo credit: Rina Andrianasolo.

“Most previous studies have suggested that the extension is localized in narrow areas around microplates that move independently of the surrounding larger tectonic plates,” Stamps said. The new GPS dataset of highly precise surface movements in East Africa, Madagascar and several islands in the Indian Ocean reveals that the disintegration process is more complex and more distributed than previously thought, according to the study, completed by Stamps. with researchers from the University of Nevada-Reno, the University of the Interior of Beira in Portugal, and the Institute and Observatory of Geophysics of Antananarivo at the University of Antananarivo in Madagascar itself.

In one region, the researchers found that the extension is spread over a large area. The region of distributed extent is approximately 600 kilometers (372 miles) wide and stretches from East Africa to entire parts of Madagascar. More precisely, Madagascar is actively breaking up with southern Madagascar moving with the Lwandle microplate – a small tectonic block – and a piece of central Madagascar is moving with the Somali plate. The rest of the island is deforming in a non-rigid way, Stamps added.

Also working on the document was a doctorate in geosciences. student Tahiry Rajaonarison, who was previously a master’s student at the University of Madagascar in Antananarivo. He assisted Stamps in 2012 in collecting the GPS data used in this study. He joined Virginia Tech in 2015 and returned to Madagascar later to collect more data as a National Geographic Society grant manager. “Leading a team to collect GPS data in Madagascar in the summer of 2017 was an amazing experience in the field,” said Rajaonarison.

The team used new surface motion data and additional geological data to test various tectonic block configurations in the region using computer models. Through a comprehensive set of statistical tests, the researchers defined new boundaries for the Lwandle microplate and the Somali plate. This approach allowed to verify whether the surface motion data is consistent with the rigid plate motion.

“Accurately defining plate boundaries and assessing whether continents diverge along zones that deform tightly or across large zones of diffuse deformation is critical to unraveling the nature of continental breakdown,” Stamps said. “In this work, we have redefined how the world’s largest continental rift is extending using a new GPS speed solution.”

The discovery of the large deformation zone helps geoscientists understand recent and ongoing seismic and volcanic activity in the Comoros Islands, located in the Indian Ocean between East Africa and Madagascar. The study also provides a framework for future studies on global plate motions and investigations into the forces driving plate tectonics for Stamps and his team.