Lava viscosity is dominated by two things: how much silica (SiO₂) has polymerised into chains in the melt, and how hot it is. This lab uses the same simplified law as the 3D version — silica raises the log-viscosity roughly linearly, heat lowers it roughly exponentially:
logη = 1 + 6·sFrac + 3·(1 − tFrac)
fluidity = 1 − (logη − 1) / 9
speed ∝ fluidity · slope
width ∝ fluidity
Fluidity then sets both the flow regime and how fast the front cools as it travels: high fluidity gives fast, wide sheet flow (pāhoehoe-like); mid fluidity narrows into a leveed channel with solid banks; low fluidity stalls before it can build any real distance. A parcel of lava emitted at the vent cools linearly with the distance it has travelled and with time spent stationary, and once its temperature drops below the ~700°C solidus it crusts over and stops advancing — visible as the front distance readout flattening out.
- Plan view — top-down view of the flow spreading from the vent; brighter parcels are hotter, dark red parcels have crusted.
- Levees — appear as thin outlines once the flow regime leaves sheet mode.
- Front-distance graph — flow-front distance from vent over time; a flattening curve means the flow has stalled.