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cph
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When did plate tectonics begin? The early Archean was essentially shallow seas, salty water early on from rifting, shield volcanoes (no sticky silicates, since no oxygen) etc. There were no deep oceans, no mountain building, no continents, since there was no plate tectonics. One could still have uplifting oceanic like plateau (like Ontang?), but no terranes drifting together, since no plates. How long would it take a crust to cool off sufficiently so that it becomes rigid enough for plates? The Earth was fully energized from mass aggregation, collisional energy, and core drop from planetesimal to proto-earth. Perhaps 1 billion years or more to cool sufficiently? Stromatolites are present at 3.5 Byrs ago, consistent with some shallow seas. If they were wide spread, might this indicate that deep oceans, high mountains, and early continent formation had not yet commenced? So was the early and middle Archean, and origin of life, largely just associated with shallow seas; very different from present plate tectonics, and resultant continents and deep oceanic environments?