Abstract Cenozoic igneous rocks south of Sumatra's Toba volcano record distinct magmatic variations across the region. The south underwent prolonged magmatic quiescence, the central region experienced a shorter pause, and the north maintained near continuous activity. Geological and geophysical data link this spatiotemporal variability to changes in slab dip angle, driven by the unevenly buoyant Wharton Ridge. However, the dynamic process of the Wharton Fossil Ridge subduction and the factors that affect it remain unclear. Using “I2VIS” thermomechanical modeling, we investigated how subduction modes depend on ridge cooling age (1–15 Ma) and continental trenchward velocity (1–3.5 cm/yr). Based on the evolution trajectory of slab dip angle ( θ ), we identify three subduction modes: flat‐slab subduction ( θ ≈ 0°), low‐angle decoupled subduction ( θ ≈ 15°), and moderate‐to‐high‐angle subduction ( θ ≥ 30°). Numerical simulations indicate that young oceanic ridges (≤5 Ma) combined with high continental trenchward velocities (≥2 cm/yr) initiate flat‐slab subduction and prolonged magmatic quiescence. In contrast, older ridges (≥7 Ma) and slower trenchward velocities (≤2 cm/yr) promote moderate‐to‐high‐angle subduction and sustained magmatism. Low‐angle decoupled subduction represents an intermediate mode, characterized by shorter periods of quiescence or diminished magmatism. Numerical results align with geological and geophysical observations. Our synthesis indicates that the spatiotemporal variations in Sumatra's magmatism during Cenozoic were jointly influenced by two concurrent factors: the cooling age of the extinct Wharton Ridge as it passed beneath the southern, central, and northern regions, and the clockwise southwestward rotation of the Sumatran Block between 50 and 30 Ma.
Li et al. (Sun,) studied this question.