Fig. 3: Plume–ridge metrics for ridge capture and ridge de-anchoring.

100 Myr time series of plume buoyancy flux, distance between the plume and ridge, and ridge spreading rates for two separate plume–ridge interactions from the 3D numerical simulation (note the y-axes have different scales). Shaded regions indicate the time window over which a mantle plume captures the spreading ridge (a–d) and where a ridge de-anchors from the mantle plume (e–h). a Buoyancy flux increases from 4500 to 6000 kg/s in the leadup to the ridge capture and peaks at 6500 kg/s as the ridge is captured. b The ridge and plume are initially spaced ~1000 km apart while the plume thermally weakens the overriding plate and causes the ridge to jump on top of the plume. c The ridge spreading rate locally increases from 5.5 to 8.5 cm/yr proceeding the ridge capture event; d angle of the plume conduit straightens from 11° to almost 0° at 45 Myr following ridge capture; e ridge de-anchoring occurs as the plume buoyancy flux diminishes from 2300 to 800 kg/s; f the ridge migrates away from the plume (up to 12 cm/yr) to a distance of 750 km; g the spreading rate of the ridge rapidly increases following ridge de-anchoring from 2 to 8 cm/yr, accelerating the rate of ridge migration; h the plume angle increases up to 14° towards the migrating ridge during de-anchoring.