junior high school lesson

7. Lava with low amount
of gas as it rises has
high viscosity that
piles up at a vent
resulting into a dome.
Lava with less silica
content is too viscous
to travel far, and
tends to break up as it
flows.
Lava with less silica
content has less silica
content has low
viscosity that it can
travel a great distance
forming a thin sheet.