Hi!How does one know if a volcano is going to give pyroclastic
emissions or not? Also, what are the options apart from evacuation if a
large city with a lot of population is going to be affected with little
warning? I mean what can individuals do apart from flee?
Archana Bhandari
Dear Archana,
It is very difficult to tell before the eruption starts if it will
produce pyroclastic material or lava flows. The gas content of the magma
is the most important factor. At the present time there are no methods
that can measure gas content of the magma. A good indication of what
might be erupted is the older deposits of the volcano. If it is mostly
lava, future eruptions will probably be lava. If it is equal amounts of
lava and pyroclastics ... it could be either one.
Your second question is tough. I'd recommend learning about the past
eruptions of the volcano so you might know what to expect. Learn the
evacuation routes of the city. Try to convince civil defense authorities
(and politicians) that plans need to be made for such a scenario (if the
volcano has erupted in such a way in the past). Depending on the type of
eruption (lahars) it might be best to move to higher ground or be aware
that the roof may collapse (ash eruptions). You might consider stocking
supplies (food, water, first-aid, radio) in case the city is cut off from
power or outside supplies. Do you have a specific volcano in mind?
Steve Mattox, University of North Dakota
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