Possible Clues:

• Oval excited about century - number in potentially explosive situation
• Vent in earth's crust
• Fifty can get inside to blow their top like this
• One expelling lava etc.
• The origin of a very heated issue
• Etna is one, and Stromboli
• Although never cool, this might make the van cool
• Mauna Loa, e.g.
• Scene of eruptions
• E.g. Vesuvius, Etna