Interaction of magma plumbing and caldera/flank collapse at Fogo volcano, Cape Verdes

• Applicant: Privatdozent Dr. Andreas Klügel
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 572143535

The evolution of volcanic ocean islands comprises eruptions, intrusions, and destructive processes including gravitational flank collapses. The hazard potential of such collapses is well recognized, but little is known about possible trigger mechanisms, feedback processes between sector collapse and magma storage, and indicators for imminent flank failure. We propose a detailed petrological study of particular samples from Fogo volcano (Cape Verde Islands) to improve our understanding of the interplay between shallow magma reservoirs, lateral flank collapse, and possible caldera formation. Fogo, one of the most active oceanic volcanoes on Earth, had undergone at least one giant flank collapse at ~68 ka during its recent volcanic evolution, resulting in a megatsunami. The temporal and geochemical evolution of the volcano before and after collapse is reasonably well established, based on key samples that include vertical profiles at the main collapse scar. These samples cover the critical period from collapse run-up to post-collapse, but detailed petrological investigations including geobarometry or diffusion chronometry are lacking. We plan to carry out such investigations of these and further key samples to reveal the evolution of the magma plumbing system before and after collapse. Specific objectives include: i) to test if magma storage beneath Fogo became shallower during the run-up to collapse; ii) to decipher if magma storage was shallow enough to cause vertical caldera collapse prior to sector collapse, a question that is currently debated; iii) to assess the role of explosive eruptions that had produced highly welded ignimbrites exposed on Fogo; iv) to test if stress changes after the giant flank collapse resulted in recognizable changes in magma storage depths and fractionation conditions. The results will provide a major step for a better understanding of the interrelationship between magma plumbing and flank collapse. Little is known about processes related to collapse of this active and potentially dangerous volcano, even though the stratigraphic framework is known and a number of well-suited samples are available. The proposed study is therefore timely, and has implications for volcanic hazards, especially for the people living on Fogo, if evolved magmas could still be stored today in shallow reservoirs and erupt.

• DFG Programme: Research Grants
• International Connection: Australia, France, Switzerland, United Kingdom
• Cooperation Partners: Dr. Raphaël Paris; Professor Dr. Sébastien Pilet; Dr. Ricardo Ramalho; Professor Dr. Axel Karl Schmitt, Ph.D.