Three Plates, One Crossroads: Modelling R-R-R Triple Junctions
What happens when three tectonic plates pull apart at the same time? At first glance, the answer might seem simple: three rifts should simply diverge from a common point. In reality, the interaction between three moving plates creates complex and dynamic pattern of deformation. Rift-Rift-Rift (R-R-R) triple junctions are among the most intriguing expressions of continental break-up. Triple junctions are in fact not simply points where three rifts meet: they are dynamic crossroads where the architecture of a new plate boundary is being built. In this regard, the Afar region, where the African, Arabian and Somalian plates meet, provides a unique example to investigate how these systems form and evolve. But how can we understand the forces and motions acting on a structure that develops over millions of years and across hundreds of kilometres?
In this talk, we will explore this question through the comparison of analogue and numerical models. By varying the relative velocities and the history of extension of the three plates, these models show how differences in plate motion can profoundly influence the geometry and position of the triple junction, producing either more symmetric, Y-shaped structures or strongly asymmetric, T-shaped patterns. Comparison with the Afar triple junction reveal an unexpected picture: neighbouring normal faults can form at high angles and remain active simultaneously, even though the overall surface motion of the crust is relatively smooth. Combining structural observations, seismicity, GNSS measurements and analogue modelling, we show how complex local deformation can emerge from the interaction of three diverging plates. Together, these results offer a window into the dynamics of continental break-up and show how geometry, motion and faulting are intimately connected.
Short Bio: Daniele Maestrelli holds a PhD in Structural Geology and is a Technologist at the Institute of Geosciences (GEO) of the National Research Council of Italy (CNR) in Florence, Italy. Since September 2024, he has also been a Contract Professor at the Department of Earth Sciences, University of Florence, where he teaches “Subsurface Geology” in the Master’s programme and “Analogue Modelling of Volcano-Tectonic Processes” in the PhD programme. With a background in structural geology, his research focuses on active tectonics and volcano-tectonic processes in both extensional (rift) and collisional settings (thrust-and-fold belts). He is particularly interested in understanding the role of volcano-tectonic structures in controlling fluid (magmatic, hydrothermal, etc.) migration, volcanic edifice evolution, and potential collapse on Earth and other planets. He conducts his research primarily through analogue modelling, fieldwork, and seismic interpretation.
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