Melt viscosity calculators
Seven calibrated models from our papers, running in your browser. Pick a melt and a temperature range: the shaded band spans the model from dry to 5 wt% dissolved water (or across composition), and the slider moves a single melt through it. Point at the chart to read η.
Same equations and parameters as the calibrated-models module of MELVIS, checked against it to machine precision. Use each model within the calibration range of its paper.
Will this melt flow, stretch or break?
A melt flows only if it has time to relax. Its relaxation time is τ = η/G∞, with G∞ ≈ 1010 Pa. Deform it faster than it can relax and it stops behaving as a liquid: first it becomes non-Newtonian, then it breaks like a glass. This is how magma can fragment during an explosive eruption.
Boundaries follow the relaxation framework of Dingwell and Webb (1989) and Webb and Dingwell (1990): non-Newtonian flow from about 10−3/τ, brittle failure from about 10−2/τ, the criterion used by Papale (1999) for magma fragmentation. Order-of-magnitude guidance, not a substitute for experiments.
MELVIS
Viscosity of any volcanic melt from its major-element composition, with uncertainty, hydrous modelling and a global map of magmas.
Open MELVISANN viscosity model
The neural-network model of Langhammer et al. (2022), trained on a global viscosity database.
Open MELVISSpreadsheets
The original Excel calculators published with each paper, for offline use and teaching.