A living cross-section of a stratovolcano. Magma viscosity, dissolved gas, vent width and slope drive the real eruption style — Hawaiian fountains, Strombolian bursts or Plinian columns — with buoyant plume height, tephra, lava-flow speed and a VEI estimate. Wait for pressure to build, or press ERUPT.
Eruption column: buoyant-plume scaling H ≈ 1.35·(Q/10⁶ W)^0.25 km (Sparks 1986). Exit velocity from chamber overpressure v = √(2ΔP/ρ). Lava flow: laminar channel speed u = ρg·sinθ·h²/(3μ) — higher viscosity or lower slope = far slower flow. Effusive vs explosive split: low μ + low gas → fountaining; high μ + high gas → column collapse into a pyroclastic density current. VEI mapped from column height and tephra volume (Newhall & Self 1982).