The Sea of Japan opens
A back-arc basin tears Japan away from Asia and swings it into its present arc.
- When
- —
- Duration
- 8 million years
- Known to
- ± 1 million years
- Era
- Miocene, Cenozoic
Rifting behind the subduction zone along the eastern margin of Asia opens the Sea of Japan through the early and middle Miocene, rotating the southwest and northeast halves of the Japanese arc in opposite directions — a motion recorded unambiguously in the palaeomagnetism of the rocks. Japan changes from a stretch of continental margin into an island arc with a deep marginal sea behind it, and acquires the tectonic configuration that makes it one of the most seismically active places on Earth.