The interpretation is based on the seismic image along profile C (Fig. 4e) as well as previous studies on magmatism46,53. (a) Between 30 Ma and 25 Ma: following lithospheric thickening due to continental collision, convective instability triggers removal of a lithosphere root and surface uplift. Asthenospheric return flow initiates ultrapotassic and adakitic volcanism in Southern Tibet. (b) Between 25 Ma and 15 Ma: magmatism persists in Southern Tibet while partial melt and heat modify the remaining thin uppermost mantle lithosphere. (c) Between 15 Ma and 10 Ma: further northward underthrusting of IL gradually shuts down the heat source of magmatism in Southern Tibet. (d) Present: Southern Tibet is completely underthrusted by IL up to the south of the JS. Magmatism in Northern Tibet is still an ongoing process.