Did plates start moving?
Isua's rocks hint at subduction 3.7 billion years ago — the earliest and most contested claim for plate tectonics.
- When
- Known to
- ± 100 million years
- Era
- Eoarchean, Archean
Some structures at Isua are read as an ancient plate boundary, with slabs of ocean floor thrust together. Others interpret the same rocks as vertical sagging of a hot, soft crust — a 'stagnant lid' regime with no plates at all. Firm evidence for modern-style subduction only appears around 2.5 billion years ago. When Earth switched from one mode to the other is among the largest open questions in geology.