How far away from a large volcano eruption do people have to be to
be safe?
Mrs. Nunn's 3rd grade
Hi Mrs. Nunn's class,
The distance you have to evacuate depends entirely on what kind of
eruption is going on. For example, Pinatubo, one of the largest recent
eruptions sent pyroclastic flows at least 18 km down its flanks, and
pumice falls were hot and heavy even beyond that. For example, pumices 7
cm across fell at Clark Air base which is 25 km from the volcano! A 7 cm
pumice won't necessarily kill you but it does mean that there is a lot of
pumice falling, and if you don't get out and continuously sweep off your
roof it may fall in and you'll get squashed.
On the other hand, the current eruption at Ruapehu is relatively small.
In fact, there were skiers up on the slopes when the eruptions commenced,
and even though they were only 1-2 km from the vent they managed to
escape. The volcanologists routinely go up on the higher slopes of
Ruapehu during these ongoing eruptions to collect ash and take photographs.
So you see, you need to know something about what you think the volcano is
going to do before you decide how far to run away. I guess if you have no
idea of what the volcano is planning, and have no idea of what it has done
in the past, you might want to be at least 25-30 km away, make sure you
have a good escape route to get even farther away if necessary, and by all
means stay out of low-lying areas!
Hopefully you won't ever have to worry about it.
Sincerely,
Scott Rowland
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