Plate tectonics is a basic facet of Earth’s geological exercise and historical past. Along with always rearranging the location of continents, in addition they play a serious position in sustaining the situations that guarantee Earth’s continued habitability. Nevertheless, Earth is the one terrestrial (rocky) planet within the Photo voltaic System with energetic plate tectonics. Whereas that is comprehensible for Mercury and Mars, that are single-plate planets which might be largely geologically inactive, on account of fast cooling of their interiors billions of years in the past. However Venus, Earth’s “Sister Planet,” has remained one thing of a thriller.
Thus far, planetary scientists have been unable to infer why Venus is geologically inactive in comparison with Earth. Nevertheless, a world crew not too long ago made a major breakthrough in our understanding of terrestrial planets and their tectonic evolution. Led by researchers from the College of Hong Kong, the crew used superior numerical fashions to determine six distinct regimes for planetary tectonics. Their analysis offers a brand new framework for classifying the vary of planetary tectonics and instruments for future planetary exploration.
The crew was led by postdoctoral fellow Dr. Tianyang Lyu, together with Professor Man Hoi Lee and Professor Guochun Zhao of the Division of Earth and Planetary Sciences at The College of Hong Kong (HKU). They had been joined by Prof. Maxim D. Ballmer from the College Faculty London (UCL), Dr. Yun Jan from the Freie Universität Berlin, Prof. Zhong-Hai Li of the State Key Laboratory of Earth System Numerical Modeling and Application, and Prof. Benjen Wu of Nanjing College. The paper describing their analysis and findings has been revealed in Nature Communications.
Snapshots of the six tectonic regimes recognized by the analysis crew. Credit score: Lyu, et al. (2025).
Tectonic regimes describe the large-scale deformation of a planet’s floor and the processes that drive it. These regimes are chargeable for shaping a planet’s geological exercise, inside evolution, magnetic area, and atmospheric composition – all of which play an enormous position in planetary habitability. For instance, the limitless biking of Earth’s lithosphere (the crust and higher mantle) is integral to the planet’s carbon cycle, together with volcanic exercise and the sequestration of carbon in carbonate rocks. This has ensured that the extent of carbon dioxide (a serious greenhouse gasoline) in our environment has remained steady over time.
In the meantime, Earth’s intrinsic magnetic area is pushed by dynamo motion within the core, the place the molten outer core counter-rotates with the planet’s stable interior core. This area prevents most cosmic rays that work together with Earth’s higher environment from reaching the floor, the place they might trigger important hurt to dwelling beings. One of the vital enduring mysteries in planetary science is why Earth experiences plate tectonics whereas Venus doesn’t. On condition that Venus is comparable in measurement, mass, and density to Earth, the identical mechanism that arrested geological exercise on Mars and Mercury shouldn’t apply.
Earth’s plate tectonic exercise is characterised by a “cell lid” regime, marked by ridges, faults, and subduction zones. The fixed biking of Earth’s lithosphere, the place ridges are pushed up, and subduction zones ship materials downward, is very similar to a conveyor belt that always refreshes Earth’s floor. For planets that don’t expertise tectonic exercise, craters and different options are preserved for eons or longer. In earlier research, researchers have proposed further tectonic regimes, akin to “sluggish lid” or “plutonic-squishy lid.”
However how these regimes relate to one another and terrestrial planets typically has remained unclear to geologists. Addressing this query, Lyu and his crew performed a statistical evaluation of mantle convection fashions to provide a listing of attainable tectonic regimes. As Dr. Lyu defined in a HKU press launch:
By statistical evaluation of huge quantities of mannequin knowledge, we had been capable of determine six tectonic regimes for the primary time quantitatively. These embrace the cell lid (like trendy Earth), the stagnant lid (like Mars), and our newly found ‘episodic-squishy lid.’ This new regime is characterised by an alternation between two modes of exercise, providing a contemporary perspective on how planets transition from an inactive to an energetic state.
Mannequin evolution and mobility dynamics of the Episodic-Squishy Lid regime. Credit score: Lyu, et al. (2025).
A serious problem within the research of geological exercise is hysteresis (or “reminiscence impact”), a phenomenon during which a planet’s tectonic state relies upon largely on its previous, not simply its current, exercise. To beat this, the crew additionally developed a complete diagram that accounted for the way all six regimes might transition from one to a different as terrestrial planets cool. This revealed that the pathways for tectonic evolution are surprisingly predictable, particularly when lithospheres weaken over time. In response to geological data, that is what occurred right here on Earth.
Because the lithosphere cooled, it turned extra liable to fracturing, resulting in the formation of plates and Earth’s present tectonic state. Since this exercise was essential to sustaining situations favorable to life as we all know it, these outcomes present a significant clue about how and when Earth turned a liveable planet. As well as, it provides a compelling rationalization for Venus’ geology, which is extremely in step with the “plutonic-squishy lid” or “episodic-squishy lid” regimes recognized of their mannequin. In these regimes, lithospheres are weakened by rising magma, resulting in regional, intermittent volcanic exercise reasonably than global-mantle-driven processes.
This presents one other fascinating takeaway of the crew’s analysis, which might present perception into the decades-long debate over volcanism on Venus. Whereas planetary scientists as soon as believed that Venus was geologically useless, current findings have challenged that view by suggesting the presence of energetic volcanoes. This research helps these findings by indicating that volcanism might persist regardless of the absence of tectonic plate exercise. In essence, the crew’s outcomes present a theoretical reference and potential remark websites for future missions to Venus. As Dr. Ballmer famous:
Our fashions intimately hyperlink mantle convection with magmatic exercise. This enables us to view the lengthy geological historical past of Earth and the present state of Venus inside a unified theoretical framework, and it offers an important theoretical foundation for the seek for doubtlessly liveable Earth analogs and super-Earths outdoors our photo voltaic system.
Additional Studying: Hong Kong University, Nature
