Summary
A new study published in Science Advances challenges traditional explanations for the formation of hot, thin ocean-continent back-arcs. Using a new, simplified modelling approach, the researchers can explain how the diverse landscapes with similar anomalies – high heat flow and an unusually thin mantle lithosphere – can form. The findings not only advance geodynamic theory but also offer insights relevant to fields such as natural resource exploration, geothermal energy, and earthquake hazard assessment. The study was led by Zoltan Erdös, researcher at GFZ Helmholtz Centre for Geosciences, together with Ritske Huismans from the University of Bergen, Norway, and co-authored by Claudio Faccenna, also from GFZ.
Background: Plate tectonics and volcanic arcs
To understand the far-reaching implications of the new study, it is important to look at some fundamental characteristics of plate tectonics, the process when Earth’s crustal plates move, collide, and submerge into Earth’s mantle. In most cases, it is oceanic crust – pushed outwards from mid-oceanic ridges – that collides with continental crust, e.g., along the western coasts of North and South America, or in the Aegean Sea between Africa and Europe. The oceanic crust sinks downwards, a process called subduction. At the collision zone, earthquakes occur due to the friction between the colliding plates. Behind the collision zone, mountains form and volcanoes appear as the sinking crust starts to melt in the hot mantle and magma rises. These volcanoes are often aligned in an arc, hence the term “volcanic arc”.
Behind the volcanic arc, highly different landscapes form – a fact that has puzzled scientists for decades. Sometimes, terrain is uplifted as is the case with the Himalaya Mountains. In other cases, the crust in the “back-arc region” sinks, getting thinner by expansion. And in yet another cases, the back-arc regions remain stable and tectonically rather quiet. Many of these regions exhibit high surface heat flow and an unusually shallow mantle-lithosphere extending hundreds of kilometres inland – characteristics, that have been difficult to explain.
New model for different landscapes behind volcanic arcs
Until now, scientists have debated competing theories to explain these anomalies, often invoking large-scale extension or convective removal of mantle material. The new model links these enigmatic features to terrane accretion – the process in which continental fragments that “float” on oceanic plate in front of the continents collide and merge with larger landmasses.
Led by postdoctoral researcher Zoltán Erdős (working at the Department of Geophysics and Space Science, Eötvös Loránd University, Budapest, Hungary at the time) and professor Ritske S. Huismans (University of Bergen, Norway), the study used state-of-the-art numerical model simulations to investigate how the gradual accumulation (“accretion”) of terranes influences the back-arc structure. They varied the subduction speed of the oceanic plate. Their findings reveal that the high surface heat flow anomalies and lithospheric thinning can emerge naturally as a result of terranes colliding with continents – without requiring widespread extension or removal of deep mantle material at the bottom of the lithosphere.
Real-World Evidence from the North American Cordillera, Anatolia, and the Aegean
The team compared their models to well-documented examples of back-arcs, including the North American Cordillera, Central Anatolia, and the Aegean Sea. These regions, despite their very different topographic features, have all experienced significant terrane accretion events in the past, and their observed geological characteristics align closely with the current study’s predictions based on the simplified model.
Why this Matters – also for resources, geothermal energy and earthquakes
This research provides a new perspective on accretionary orogens and back-arcs, showing that terranes colliding with continents can naturally produce the high heat flow and shallow lithosphere-asthenosphere boundary observed in many back-arcs. While other processes may also contribute to these features, the study demonstrates that terrane accretion alone is sufficient to explain them, offering a valuable framework for interpreting past and present subduction systems worldwide. The findings not only advance geodynamic theory but also offer insights relevant to fields such as natural resource exploration, geothermal energy, and earthquake hazard assessment.
About the Authors
This research was conducted by Zoltán Erdős (currently at GFZ Helmholtz Centre for Geosciences, Potsdam, Germany), Ritske S. Huismans (Department of Earth Sciences, University of Bergen, Norway), Sebastian G. Wolf (Department of Earth Sciences, University of Bergen, Norway), and Claudio Faccenna (GFZ Helmholtz Centre for Geosciences, Potsdam, Germany and Department of Science, University Roma Tre, Roma, Italy). Their work builds on previous studies exploring the dynamics of subduction zones and continental deformation.
For more information, see the original publication:
Erdős, Z., Huismans, R. S., Wolf, S. G., Faccenna, C. (2025): Terrane accretion explains thin and hot ocean-continent back-arcs. - Science Advances, 11, 17.
https://doi.org/10.1126/sciadv.adq8444