Volcanic activity in the Rift Valley and hominid evolution

Volcanic activity in the Rift Valley over the past four million years has not been continuous but has occurred in bursts, characterised by brief periods of intense explosive activity interspersed with quieter or less active phases. This finding emerges from research by the University of Florence and the Institute of Geosciences and Earth Resources of the National Research Council of Florence (CNR-IGG), in collaboration with universities in Ethiopia, France, and the United Kingdom. The study, published in the journal Communications Earth & Environment from the Nature group, provides for the first time a detailed analysis of the volcanic evolution of the Rift Valley in Ethiopia ("Pulsatory volcanism in the Main Ethiopian Rift and its environmental consequences" https://doi.org/10.1038/s43247-024-01703-1).

“Through data collected during multiple field campaigns and laboratory dating of numerous volcanic rock samples, we identified a primary period of intense volcanic activity between 3.4 and 3.8 million years ago, followed by four additional phases of significant volcanism,” explains Giacomo Corti of CNR-IGG. “Each of these phases included large-scale explosive events, some of which produced volcanic deposits tens of metres thick.” These events significantly reshaped the landscape, rendering vast areas inhospitable for extended periods and potentially impacting the global climate.

“These events occurred during a crucial period for hominid evolution, an era when Australopithecines, like the famous ‘Lucy,’ were giving way to the first species of the genus Homo, our closest ancestors,” adds Raffaello Cioni from the University of Florence’s Department of Earth Sciences. “It is highly likely that these events had a profound impact on altering the environment and living conditions in this critical area for human evolution.”

The African Rift Valley is renowned for its extraordinary biodiversity and is considered one of the most important sites for paleoanthropological discoveries. Spanning thousands of kilometres, this system of linear valleys is the result of the ongoing separation of the African continent in its eastern region. It is a geologically fascinating area where volcanism, earthquakes, and crustal fracturing reveal the powerful tectonic forces shaping the planet and potentially influencing the evolution of our ancestors.

“The findings of this study represent a significant step forward in understanding the geodynamic processes underlying the formation of continental rift valleys,” concludes Zara Franceschini from the University of Florence. “Our work demonstrates how these processes can evolve in highly irregular temporal patterns, with profound consequences for the morphology, climate, and environmental conditions of vast regions of the planet.”