New 'Episodic‑Squishy Lid' Tectonic Regime May Rewrite How Planets Become Habitable

Scientists report a newly identified tectonic regime — the "episodic‑squishy lid" — that could change how we understand the evolution of rocky planets. Using advanced geodynamic simulations, researchers mapped six distinct tectonic behaviors and found a previously unrecognized state that sits between classic plate tectonics and a stagnant lid.

This regime is characterized by long stretches of relative calm interrupted by sudden, regional episodes of tectonic motion. Unlike a permanently stagnant lid, the episodic‑squishy lid allows the lithosphere to weaken intermittently through processes such as intrusive magmatism and regional delamination, temporarily softening the crust before it re‑hardens.

The new framework helps explain how early Earth may have transitioned from an inactive outer shell to the sustained plate tectonics we see today. The models suggest a gradual pathway: as the planet cooled, its lithosphere became more fracture‑prone under specific physical mechanisms, with a squishy‑lid phase priming the surface for eventual continuous plate motion.

The study also clarifies the so‑called "memory effect," the idea that a planet's tectonic behavior is shaped by its past. As a lithosphere weakens over time, transitions between tectonic regimes become more predictable, meaning a planet's earlier conditions help determine its later tectonic fate.

Crucially, the simulations reproduce Venus‑like surface patterns when the planet is placed in an episodic or plutonic squishy‑lid regime. Although Venus is similar in size to Earth, it shows little evidence of plate tectonics and instead bears signs of widespread volcanism and unique features called coronae. In the models, periodic magmatism and mantle plumes weaken the surface without producing coherent plates—matching many observations of Venus.

"Geological records suggest that tectonic activity on early Earth aligns with the characteristics of our newly identified regime," said Guochun Zhao of the Chinese Academy of Sciences. "As Earth gradually cooled, its lithosphere became more prone to fracturing under specific physical mechanisms, eventually leading to today's plate tectonics."

"Our models intimately link mantle convection with magmatic activity," said Maxim Ballmer, associate professor of geodynamics at University College London. "This gives us a unified theoretical framework to compare Earth's history and Venus's present state, and it helps guide the search for habitable Earth analogs and super‑Earths."

Understanding tectonic regimes matters because lithospheric behavior controls the cycling of water and carbon dioxide between a planet's surface and interior. These exchanges influence a planet's magnetic field, atmosphere and long‑term climate stability — all key factors for habitability. By mapping likely transition pathways as planets cool, the research offers new criteria for prioritizing exoplanet targets for future observations.

The findings were published on Nov. 24 in the journal Nature Communications.