Environmental Engineering Reference
In-Depth Information
to damage vegetation on a global scale. In their model, global surface temperatures
change between
4.5
C when averaged over a decade of eruptive
activity and return to background values within less than 50 years. These cooling
estimates are at the lower end of previous estimates but nonetheless represent a
substantial climate perturbation (see also
Chapter 13
; Thordarson and Self,
1996
).
Schmidt
et al
. (unpublished) conclude that better constraints on the frequency and
duration of individual eruptions as well as hiatus periods are needed to fully
quantify the magnitude and duration of the climatic and environmental effects.
-
3
C and
-
11.5 Summary
CFB provinces appear to form within 1 to 3 million years, with many showing
evidence for one or more pulses of increased magma production and eruption
lasting from 1 million to as little as a few 100,000 years. Each of these pulses
features tens to hundreds of individual eruptions, each potentially producing up
to 10,000 km
3
(more usually 1,000
5,000 km
3
) of predominantly p
-
ā
hoehoe lava.
eld produced a 1,300 km
3
The eruption of the Roza
ow-
lava
ow-
eld over a
period of at least 10
-
15 years (Thordarson and Self,
1998
) and more recent work
on other CRBG
elds generally agree with this duration (Vye-Brown
et al
.,
2013
). For other CFB provinces, we can only infer eruption durations of decades to
centuries by analogy, backed up by the dominance of basaltic
ow-
-
andesitic p
ā
hoehoe
lava
elds.
CFB eruptions could have injected gases into the stratosphere, if not semi-
continuously, then intermittently during decade-long eruptions. Measurements
suggest that the Roza eruption released about 12,000 Mt of SO
2
over its course
(Thordarson and Self,
1996
) and, in general, it appears that every 1 km
3
of magma
emplaced during a CFB eruption releases 6
ow-
1.7 Mt of SO
2
.Themajorityof
magmatic gas species released during CFB volcanism have potential environmental
impacts. However, the fate of these volatiles and therefore the magnitude of their
environmental effects is poorly constrained at present. For example, further work is
needed to understand the atmospheric burdens, atmospheric lifetimes and climatic
impact of the magmatic sulfur- and halogen-bearing species released during a typical
CFB eruption. Recent progress has included the use of global climate and aerosol
models (Black
et al
.,
2014
;Schmidt
et al
., unpublished). Better CFB magmatic
volatile release scenarios are needed to facilitate further such modelling efforts
sedimentary bedrock during the emplacement of some CFB provinces may be an
important additional
flux of volatile species into the atmosphere (see also
Chapters 10
and
20
). These interactions are speci
c to each different province and further work is
needed to constrain their magnitude on a case-by-case basis.
