Suture zone

A suture zone is the linear boundary where two previously separate tectonic plates have collided and welded together, marking the final closure of an ocean basin. It is not a simple line on a map but a complex belt of intensely deformed rock — ophiolites, mélanges, high-pressure metamorphic rocks, and sheared sediments — that records the violent negotiation between converging lithospheres. The suture is the scar left by plate tectonics when the wound has healed, and like biological scar tissue, it is often the strongest part of the healed structure. The Indus-Yarlung suture in the Himalayas is perhaps the most famous example, marking where the Tethys Ocean closed and India fused to Eurasia.