Onset and Evolution of Plate Tectonics: Geodynamical Constraints

Abstract

Today, plate tectonics dominates the large-scale dynamics of the Earth. But a large number of observations suggests that Earth's tectonics operated differently in the past. Earth's interior was 150–250K hotter than today, which affects the density and strength of the tectonic plates, and modeling studies have illustrated how this must have significantly changed or complicated the plate-tectonic process we know today. Such theoretical considerations, as well as observations from the oldest preserved rock record, around 4 billion years ago, suggest that vertical, stagnant-lid, squishy-lid, or heat-pipe tectonics may have dominated in the past. Several key characteristics of modern-day plate tectonics (such as ophiolites, high-pressure metamorphic rocks, and cold geotherms) were rare or absent in the past, and gradually evolved or appeared in time. This suggests that, since the early Archaean, Earth's tectonic regime evolved through various embryonic stages of plate tectonics, in which plates were young and hot, trenches did not move much, and subduction was perhaps intermittent and episodic, into a planet with fully developed, robust plate tectonics as we know it today.