A reinterpretation of the past 2.5 billion years of Earth’s tectonic history: Two episodes each of plate and single-lid tectonics

This paper reinterprets the past 2.5 billion years of Earth’s tectonic history as four alternating episodes when plate tectonics dominated and when it did not. Solar System exploration over the past 50 years reveals that 75% of the four actively convecting silicate bodies (Venus, Earth, Mars, and Io) do not have plate tectonics. Instead, their deformed and magmatically active lithospheres are better characterized as coherent, if deformed, single lids. I identified geologic indicators of plate tectonic regimes and single-lid tectonic regimes, used published compilations of these, and worked backward in time to 2.5 Ga. This analysis reveals four distinct tectonic episodes, two each of plate tectonics and single-lid tectonics. The youngest is the current episode of plate tectonics (PT2), which began at ca. 800 Ma. PT2 was preceded by an ∼600-m.y.-long episode of single-lid tectonics during the Mesoproterozoic (SL2). SL2 was preceded by an ∼300-m.y.-long episode of plate tectonics in mid-Paleoproterozoic time (PT1). The oldest post-2.5 Ga tectonic episode was an enigmatic ∼200-m.y.-long interval of single-lid tectonics in early Paleoproterozoic time (SL1). Each episode is separated from earlier and later episodes by transitional periods lasting 100−200 m.y. This reinterpretation of Earth’s post-2.5 Ga tectonic history helps to explain why Earth’s mantle is warmer than it would be if it had cooled as rapidly as it is cooling today—that is, if plate tectonics operated continuously during this time. It also moots the question of “When did plate tectonics start?” and suggests that a better question is, “How far back in time can we confidently reconstruct Earth’s tectonic history?” The reframed question provides new research opportunities and insights into mineralization, climate, and biologic evolution, and opens the door to a better understanding of Archean, especially Late Archean, tectonics.