An underwater hotspot volcano erupts repeatedly, piling up lava flows on the seafloor until the cone breaches the surface and becomes an island — the same process that built Hawaii and Surtsey. Technically, terrain is a 160×160-segment PlaneGeometry whose vertex heights are displaced each frame by a radial cone profile plus a cheap sine-based hash noise function for rocky detail, with per-vertex vertex-colors driven by elevation relative to sea level. Molten rock and steam are two independent GPU point-sprite particle systems (lava: gravity-integrated ballistic arcs with age-based hot→mid→cool color lerp; steam: buoyant puffs spawned wherever lava crosses the waterline) rendered with additive-blended PointsMaterial. The ocean surface is a separate ShaderMaterial plane with vertex-displaced sine waves and depth-based color mixing.