The two most important properties of lava are its viscosity, and the amount of gases dissolved in the liquid rock. Let's look at each of these separately. Viscosity is a term that describes the fluidity or runniness of the lava. Some lavas are very runny, not quite like water, but more like warm honey or hot wax.When these lavas erupt, they flow for large distances before cooling enough to turn solid.olcanic eruptions may be quiet outflows of lava which are so peaceful that one can stand close enough to toss in pebbles (or leis; see figure) or so explosively violent that they blow mountains apart and blast everything within a hundred miles to smithereens (not recommended for close observation).