Expert volcanologist Dr. Stanley Williams answered the following questions for Scholastic Network.
When a volcano erupts, does it ever run out of magma? How does it "refuel" so it can erupt again?
A volcano occurs where there is magma rising from the mantle and burning its way through the crust. Volcanoes do run out of magma. That usually means that they become quiet and inactive for ten to 100 years until a new batch of magma comes up from deep inside the earth. This means that people get fooled by the quiet volcano, so they make the big mistake of thinking that it might be "extinct," which really means dead for all time. For volcanoes, it is dangerous to think that — volcanoes are just waiting for new magma to cause another eruption.
How does magma form?
Magma forms because the rocks are at high temperature and pressure deep inside the earth. Actually, it is only a small percentage of the rocks that actually melts because it requires so much energy to melt rocks.