A mantle plume is a narrow column of unusually hot rock rising from deep in the mantle. Where it melts beneath the base of a moving tectonic plate, it feeds a volcano — but the plume itself stays roughly fixed relative to the deep mantle while the plate glides overhead. This map view renders the scene in the plate-fixed frame (the grid is the plate, held still), so the plume's melting point appears to migrate across it in the direction exactly opposite the plate's true motion, at the same speed:
v_hotspot(apparent) = −v_plate
d = v · t (age-distance rule: seamount age ∝ distance from the active hotspot)
Every ~15 km of apparent hotspot travel, a new edifice begins growing wherever the melt supply is close enough to feed it. Once the plate carries it more than ~45 km from the plume, magma supply is cut off and it goes extinct. As the surrounding lithosphere then cools and thickens with age, it subsides — the classic half-space cooling relationship:
subsidence(age) ≈ k · √age
Young extinct volcanoes still stand above the waves; older ones (further down the chain) sink below sea level and become flat-topped guyots — exactly what happens along the real Hawaiian–Emperor seamount chain, whose famous ~60° bend around 47 million years ago is read directly from a change in the track's apparent heading, just as steering the direction slider mid-run bends the track here. Steering while the simulation runs, or after a Reset, always regrows the chain from a clean, unmelted slate. Circle size shows each edifice's height above its subsided base; the plume vent itself pulses at the head of the track.
- Plate speed / direction — sets the true plate-motion vector; the hotspot track is its mirror image.
- Magma flux — scales how tall each edifice grows before its magma supply is cut off.
- Simulation speed — how many million years elapse per real second.