In the Deadly Shadow of Vesuvius

In recent years, volcanologists probing Mt. Vesuvius with electric currents have discovered a huge rock plug jammed into the the mountain's "conduit"-the 100-foot-wide pathway leading from its deep magma chamber to the surface. Is this good news or bad news for the people living in nearby Naples, Italy?

(Check out this week's website, In the Deadly Shadow of Vesuvius. It's packed with helpful hints.)

1. Good news, because the presence of a protective plug indicates that Vesuvius is unlikely ever to erupt again.
   
   
2. Good news, because the presence of a plug indicates that the once-threatening magma deep below Vesuvius has cooled and hardened into a dormant, harmless mass.
   
   
3. Bad news, because the plug's presence indicates that the next eruption is likely to be effusive-producing scorching, deadly rivers of lava—rather than a relatively harmless pyroclastic flow.
   
   
4. Bad news, because the plug's presence indicates that the next eruption is likely to be explosive—producing a deadly, avalanche-like pyrocastic flow of gas, rocks, and hot ash—rather than a relatively harmless effusive eruption of hot but slow-moving lava.