There are various types of volcanic eruptions wherein one of which is the Strombolian eruptiondriven by the bursting of gas bubbles within the magma which grow large enough to rise yet still weak enough to cause destruction and harm.
The relative passivity of Strombolian eruptions, and its non-damaging nature to its source vent allow Strombolian eruptions to continue unabated for thousands of years, and also makes it one of the least dangerous eruptive types. 
