File:Viscosity of magma EN.svg - Wikipedia

English: Viscosity of magmas of different compositions and temperatures. Coloured lines represent magma with the same temperature, but different composition.

The vertical axis has the logarithm of the viscosity η, the horizontal axis the mass percentage of silica (SiO₂). Names for effusive rock types of the same composition are indicated in the diagram.

Sources:

• Hess, P.C.; 1989: Origin of Igneous Rocks, Harvard University Press, Cambridge.
• Winter, J.D.; 2001: An introduction to igneous and metamorphic petrology, Prentice-Hall.