Viscosity Viscosity is a measure of the internal resistance of a liquid body to flow. It is the inverse of mobility or fluidity. Water is highly fluid and has a very low viscosity, whereas honey, or heavy machine oil is much more viscous.
Viscosity varies with temperature and composition of liquid.
Viscosity increases with an increase in SiO2 in a magma. As shown in the figure above, rhyolitic magma has a higher viscosity than basaltic magma due to the higher SiO2 content of rhyolite. Density Density is the mass per unit volume of a substance. The only information we have is from whole rock chemistry. So, we calculate the density of a rock as the sum of the masses for all components of a substance divided by the sum of all their volumes.