Reply #3: Yes, I believe it depends on the composition of the magma [View All]

[daleo]

Some volcanoes erupt rarely, but very explosively (e.g. Mt. St. Helens), while others erupt fairly frequently but not that dramatically (such as Etna). I think it depends on the viscosity of the rock and the amount of gas that can be trapped.

Although Etna has been variable throughout history.

http://boris.vulcanoetna.com/ETNA_blow.html