How hot is it close to a lava stream?
Orianna and Tom
Hi Orianna and Tom,
It depends on how close you are, what kind of lava flow it is, and whether
you are upwind or downwind. For example, the most approachable lava is
pahoehoe. This is because each toe forms an insulating skin seconds after
emerging on the surface. This skin is at first flexible and then hardens,
but even when flexible it is a good insulator. This serves to keep the
interior of an active pahoehoe toe hot and fluid but also prevents you
from getting burned by the radiant heat. If the wind is at your back, you
can easily approach long enough and close enough to get a sample with a
hammer. It is still hot, and unless you are well-protected you can only
be that close for a minute or so. You also notice that as soon as you
peel the skin off to get at the molten interior, the heat goes way up.
This is heat that you can't stand, you have to get back otherwise blisters
start to form. It is hot enough that you can't accidentally step on
active lava.
Skylights into lava tubes on pahoehoe flows are quite hot, and have to be
approached from upwind. They are so hot that the air shimmers over them
so they too are hard to miss. They are dangerous not as much because of
the radiant heat from the lava inside but because of the super-heated air
coming out. You have to be really careful that the wind doesn't shift,
and many a volcanologist (at least this one, anyway) has gotten singed hair,
eyebrows, etc. when the wind changed.
An 'a'a flow, on the other hand is terrible to work near. Instead of a
relatively continuous skin, 'a'a flows have discontinuous layers of
clinker, and a huge amount of radiant heat escapes from between the
clinker. 'A'a flows also move faster so you really have to be quick on
your feet if you want a sample. Additionally, 'a'a flows tend to form
open channels rather than lava tubes. The channels can sometimes have
completely incandescent surfaces because they are flowing so fast that
any skin that forms is immediately torn or sunk. I remember once flying
over a large channel in a helicopter. We must have been at least 200-400
meters above the flow, but as soon as we were over the channel we could
immediately feel the radiant heat through the windows! I would bet that
nobody has been downwind of an active 'a'a channel.
Hopefully this gives you some ideas. You'll just have to come over to
Hawai'i (or visit some other active volcano) if you want the real experience.
Sincerely,
Scott Rowland, University of Hawaii
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