Environmental Engineering Reference
In-Depth Information
(e.g. Robock
et al
.,
2009
; Timmreck
et al
.,
2012
; Segschneider
et al
.,
2013
; see
also
Chapter 13
). These studies highlight the signi
cance of dynamical integration
of components of Earth system models, of the prevailing climate state and sensi-
tivity at the time of eruption, and of representing adequately the microphysical
processes occurring in volcanic aerosol clouds. In the case of the Youngest Toba
Tuff eruption, some of the models (e.g. Robock
et al
.,
2009
) have assumed a
very large sulfur release (200 times greater than that of Mount Pinatubo in 1991).
However, petrological considerations point to the Youngest Toba Tuff magma
having been relatively low in sulfur content (Scaillet
et al
.,
1998
; Chesner and
Luhr,
2010
).
2.6.1 Scenario for a future super-eruption
We can also only speculate when and where the next super-eruption might occur.
Toba, Yellowstone or Taupo all remain possible candidates, raising the possibility
of future super-eruptions in the tropics or mid-latitudes of both north and
south hemispheres. Seismological investigation at Yellowstone revealed a
shallow magma reservoir of more than 4300 km
3
in total volume, a third of which
is molten (Chu
et al
.,
2010
). It is also possible that a super-eruption could occur
at a volcano that has not experienced one previously.
But how would a super-eruption in the not-too-distant future affect us? Much
would depend on the state of preparedness. No rigorous attempts have yet been
made to model risk scenarios of such an event, though there have been a number of
summaries of generic consequences (e.g. Self,
2006
; Oppenheimer,
2011
; Dono-
van and Oppenheimer,
2014
) based on inferences from studies of the Youngest
Toba Tuff and other eruptions, and the findings of climate and Earth system
models. For instance, pyroclastic currents from an
M
8 or 9 event can be expected
to extend up to 100 km radially from the volcano. These would engulf an area of a
few tens of thousands of square kilometres in incandescent pumice to a depth of up
to 200 m. The case of the eruption of Mont Pelée in 1902, in which approximately
29 000 perished, with almost every last inhabitant of the town of St Pierre killed,
demonstrates that the chances of surviving exposure to pyroclastic currents can be
vanishingly small. Beyond the fringes of a super-eruption
s ignimbrite deposits,
there may be some chances of initial survival, though many would subsequently
die from exposure, burns and other injuries.
A much wider zone will be affected by thick tephra fallout. Where more than
0.5 m of ash accumulates, substantial building damage can be anticipated, likely
claiming many victims. Power lines would be brought down and telecommuni-
cations generally compromised by the electromagnetic effects of airborne ash
(e.g. Wilson
et al
.,
2012
). Air quality and visibility during and for a long time
'
