A simplified magma-chamber model drives four monitoring signals a real volcano observatory watches:
- Chamber pressure — rises with the magma supply rate and bleeds off through conduit degassing: dP/dt = supply·A − leak·P.
- Seismicity — micro-earthquake rate tracks the rate of pressure change (rock fracturing as the chamber inflates), plus a stochastic background rate.
- SO2 flux — scales with chamber pressure, since dissolved gas exsolves faster under higher pressure.
- Ground deformation — relaxes toward a target proportional to pressure, modelling the slow inflation/subsidence a tiltmeter or GPS station would record.
When pressure exceeds the conduit-strength threshold, an eruption releases pressure rapidly while seismicity, gas and the visible plume spike — then the chamber begins refilling. The alert level blends all three signals (50% pressure ratio, 30% seismicity, 20% deformation) into the four-color scale real observatories use: Green → Advisory → Watch → Warning.