Geyser pressure dynamics — 2D conduit cross-section

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What to try
  1. Watch the white boiling-point ticks: the deep water is far hotter than 100 C yet does not boil, because the water above squeezes it.
  2. Raise the heat input: eruptions come more often because the deep water reaches its boiling point sooner.
  3. Lower the recharge temperature: the refilled column is cold, so the cycle gets longer.
  4. Increase the depth: the bottom boiling point rises (about 133 C at 20 m) and the jets get taller.
The science

A geyser conduit is a tall water column heated from below. The pressure at depth z is hydrostatic and sets the local boiling temperature through the saturation curve (Antoine fit to steam-table data):

P(z) = P0 + ρ g z,   log10 Psat = A − B/(C + T),   Tboil(z) = Tsat(P(z)) Eruption when T(z) > Tboil(z); flash enthalpy ΔH = m cp (T − Tboil); jet: ½ M v² = η ΔH,   h = v² / 2g

The model discretises the conduit into 40 layers, heats the lowest three at the set power, mixes heat by an eddy diffusivity, and refills the ejected column with cool water. When the deepest water becomes superheated it flashes, the column above it is thrown out, the pressure on the water below drops, and the cascade continues until no layer is above its boiling point.

Simplifications: one-dimensional lumped model; the energy-to-jet efficiency η is a tuning parameter, not derived; no two-phase flow, bubble nucleation kinetics, non-condensable gases or side chambers; recharge is instantaneous. It is a teaching model of the mechanism, not a predictor for a real geyser.