An international research team has made a groundbreaking discovery that sheds light on the tectonic evolution of terrestrial planets, providing insights into why Earth and Venus have developed such different geological characteristics. The study, published in Nature Communications, identifies six distinct tectonic regimes, including a newly classified regime termed the “episodic-squishy lid.”
The research was led by scientists from the Department of Earth and Planetary Sciences at The University of Hong Kong (HKU). Key contributors include postdoctoral fellow Dr. Tianyang Lyu, Professor Man Hoi Lee, and Professor Guochun Zhao. Their findings provide substantial evidence regarding the evolution of Earth’s plate tectonics while also offering a theoretical framework to better understand the geological features of Venus.
Unveiling Tectonic Regimes
Tectonic regimes refer to the processes that cause large-scale deformations of a planet’s surface. These processes are crucial in shaping a planet’s geological activity, internal evolution, magnetic field, atmospheric composition, and potential to support life. One of the most intriguing questions in planetary science has been the contrast between Earth’s active plate tectonics and Venus’s markedly different geological history.
The researchers classified the six tectonic regimes through advanced numerical models, capturing the diversity of tectonic activities. For instance, Mars exhibits a “stagnant lid” regime, resulting in a largely immobile surface. In contrast, Earth operates under a “mobile lid” regime, characterized by mid-ocean ridges, subduction zones, and transform faults. These tectonic activities have played a critical role in stabilizing Earth’s atmosphere and climate over extensive periods, thus supporting the evolution of life.
The study highlights that while previous research suggested tectonic regimes such as the “sluggish lid,” the relationships among these regimes remained poorly understood. Dr. Lyu explained, “Through statistical analysis of vast amounts of model data, we were able to identify six tectonic regimes quantitatively.” This includes the mobile lid, stagnant lid, and the newly identified episodic-squishy lid, which alternates between two modes of activity, presenting a new perspective on planetary transitions from inactivity to activity.
Understanding the ‘Memory Effect’
A significant challenge in predicting a planet’s tectonic evolution has been the concept of the “memory effect,” where a planet’s tectonic state is influenced by both current conditions and its historical context. Professor Lee noted, “Our models reveal that this ‘memory effect’ is not insurmountable.” Particularly for Earth, where the lithosphere weakens over time, transitions between tectonic regimes can be predicted with surprising accuracy.
The research team developed a comprehensive diagram illustrating the six tectonic regimes under various physical conditions, revealing potential transition pathways as a planet cools. Professor Zhao, an Academician of the Chinese Academy of Sciences, emphasized the importance of these findings. He stated, “Geological records suggest that tectonic activity on early Earth aligns with the characteristics of our newly identified regime.” As Earth cooled, its lithosphere became increasingly fractured due to specific physical mechanisms, eventually leading to the plate tectonics we observe today.
The study also provides compelling insights into the geology of Venus. The models suggest that some of Venus’s surface features, including the circular “coronae,” align with the episodic-squishy and plutonic-squishy lid regimes. In these regimes, magmatic intrusions weaken the lithosphere, resulting in localized tectonic activity driven by mantle plumes rather than by global plate boundaries.
Co-author Professor Zhong-Hai Li from the University of Chinese Academy of Sciences remarked on the significance of comparing model results with geological observations of Venus. He noted, “This provides important theoretical references and observational targets for future Venus missions.”
The research establishes a new framework for understanding planetary tectonic diversity, offering valuable tools for future explorations. Dr. Maxim D. Ballmer from University College London, another co-author, concluded, “Our models intimately link mantle convection with magmatic activity, which allows us to view the long geological history of Earth and the current state of Venus within a unified theoretical framework.”
This comprehensive study not only advances our understanding of tectonic processes but also informs the search for potentially habitable Earth-like planets and super-Earths beyond our solar system.
