Geodynamica

How the formation and breakup of supercontinents drive environmental shifts remains a fundamental question, but piecemeal deep-time records prevent an answer based on observations. Here we present the first simulation of an Earth-like planet integrating geodynamics, climate, and surface processes to assess how solid Earth dynamics regulate environmental change. We show that mantle flow governs surface conditions through two coupled pathways: true polar wander (TPW) and seafloor spreading rate. During supercontinent assembly, a large-scale mantle flow draws continents together and, through TPW, aggregates the landmasses toward the equator, while seafloor production decreases and the seafloor ages. The larger tropical land area increases planetary albedo and continental weatherability, while reduced seafloor spreading lowers mantle degassing; together these effects suggest a cooling of the atmosphere while the mantle warms. During breakup, the switch to smaller-scale mantle flow reverses both pathways: continents drift as seafloor rejuvenates, lowering tropical albedo and weatherability while increasing degassing and sea level, which together warm the atmosphere as the mantle cools. These internally generated, mantle-driven shifts reproduce key features of Pangea on Earth, providing a mechanistic framework linking deep Earth dynamics to climate and, ultimately, to conditions for life.