Geoscience Reference
In-Depth Information
7.4 Recent and active volcanoes
You need to take special
care and be extra vigilant
when working on or near an
active volcano.
Active and recently active volcanoes allow you to see igneous
rocks in the making, or at least before they have been changed
by weathering, burial or other processes. They are places where
processes can be studied on scales ranging from molecular
chemistry (when volcanic gases mix with the atmosphere) to
the deformation of a stratocone volcano under its own weight.
There is space here to mention only a few general principles.
7
7.4.1 Equipment and safety
Your safety equipment should include a hard hat even if you
do not intend to work close to any cliffs, to offer head
protection if an explosive eruption occurs. The ground may be
unstable (especially on fresh pahoehoe and on
'
a
'
a of any age),
so it is wise to carry a long stick for support and (if necessary)
probing. You should also wear tough trousers and gloves of
suitable material for protection against cuts and burns, and
which will not melt when exposed to heat (Figure 7.23). If you
expect to be working near fumaroles you should carry a gas
mask capable of fi ltering out acid gases such as sulfur dioxide.
You should NEVER risk putting yourself in either of the
following situations, but here is some advice that might save
your life if you get caught.
•
If volcanic bombs start falling towards you, do not turn and
run. It is better to stand and face the bombs, preferably
somewhere where you can dodge without tripping over.
Watch the bomb-fall carefully, and if you are sure that one
is headed for you, step aside so that it misses you.
•
If a pyroclastic surge is coming your way, you will not be
able to outrun it, although you may be able to escape
sideways out of its path. If not, cover as much of your body
as you can, especially your face, and get down as low as
you can in a hole or behind a large rock. While the fl ow is
passing, hold your breath for as long as possible so you
don't sear your lungs by inhaling hot gas and ash.
Figure 7.23
The shelly skin of
this recent pahoehoe fl ow gave
way under the weight of this
volcanologist. Wisely, he is
wearing long trousers (rather than
shorts) that would have protected
his shins if he had stumbled into
the sharp, glassy rim (Kilauea,
Hawaii). A far worse accident
would have been to have broken
through the roof over an active
lava tube. (David A. Rothery, The
Open University, UK.)
Sampling and measuring equipment will depend on the nature
of your study. Infrared thermometers can record temperatures
for studying vent processes or lava fl ow rates (Figure 7.24,
p. 160), there are various ultraviolet or infrared sensors for
studying volcanic gases, and of course you may wish to collect
samples of rock. Downwind of an explosive vent, something as
simple as an aluminium baking tray can usefully be laid out to
catch scoria fall-out, for studies of crystallization and
vesiculation changes during the course of an eruption.
