An international research team has made a pivotal advancement in understanding the tectonic evolution of terrestrial planets, revealing six distinct tectonic regimes. This breakthrough, based on sophisticated numerical models, identifies a novel regime termed the “episodic-squishy lid.” The study provides significant insights into the origins of Earth’s plate tectonics and offers a theoretical framework for interpreting the complex geological features of Venus. The findings were published in the journal Nature Communications.
Classifying Tectonic Regimes
Tectonic regimes refer to the large-scale deformation processes of a planet’s surface layers. The classification of these regimes is crucial as they influence geological activity, internal evolution, magnetic fields, atmospheric compositions, and even the potential for life on a planet. One of the most intriguing questions in planetary science is why Earth exhibits active plate tectonics while Venus, often referred to as its “sister planet,” shows markedly different geological characteristics.
The research highlights that different planets can exhibit various tectonic regimes. For instance, Mars operates under a “stagnant lid” regime, resulting in a largely immobile surface that retains ancient impact craters. In contrast, Earth functions within a “mobile lid” regime, characterized by mid-ocean ridges, transform faults, and subduction zones. These boundaries lead to geological phenomena such as earthquakes and volcanism, which have been pivotal in stabilizing Earth’s atmosphere and climate over millions of years.
Dr. Tianyang Lyu, the first author of the paper and a postdoctoral fellow at The University of Hong Kong, stated, “Through statistical analysis of vast amounts of model data, we were able to identify six tectonic regimes for the first time quantitatively.” The identified regimes include the mobile lid (like modern Earth), stagnant lid (like Mars), and the newly discovered episodic-squishy lid, which is characterized by alternating modes of tectonic activity.
Understanding Tectonic Evolution
One of the significant challenges in predicting a planet’s tectonic evolution has been the concept of the “memory effect.” This phenomenon indicates that a planet’s tectonic state depends not solely on its current conditions but also on its historical context. Professor Man Hoi Lee emphasized that the models reveal this effect is manageable. He noted, “Especially on an evolutionary path where the lithosphere weakens over time—as is the case for Earth—the transition between tectonic regimes can be surprisingly predictable.”
The research team developed a comprehensive diagram that maps all six tectonic regimes based on various physical conditions, illustrating potential transition pathways as a planet cools. Professor Guochun Zhao, an Academician of the Chinese Academy of Sciences, added, “Geological records suggest that tectonic activity on early Earth aligns with the characteristics of our newly identified regime.” This insight helps explain how Earth became a habitable planet as its lithosphere evolved.
The study also sheds light on the geological mysteries of Venus. The researchers found that certain surface features, such as the circular “coronae” measuring over 1,000 km in width, align with the episodic-squishy lid regime. In this regime, magmatic intrusions weaken the lithosphere, leading to intermittent tectonic activity primarily driven by mantle plumes rather than global plate boundaries.
Professor Zhong-Hai Li from the University of Chinese Academy of Sciences, a co-author of the study, expressed enthusiasm about comparing model results with geological observations of Venus. He stated, “This provides important theoretical references and observational targets for future Venus missions.”
The research lays a foundational framework for understanding planetary tectonic diversity and offers tools for future exploration. Dr. Maxim D Ballmer from University College London, another co-author, stated, “Our models intimately link mantle convection with magmatic activity, allowing us to view the long geological history of Earth and the current state of Venus within a unified theoretical framework.”
With these findings, the team not only advances our understanding of Earth and Venus but also provides crucial insights that could guide the search for potentially habitable Earth analogs and super-Earths beyond our solar system.
