Environmental Engineering Reference
In-Depth Information
sulfur release increases, aerosols form larger particles (with lower optical depth per
unit mass and more rapid settling rates), effectively limiting the magnitude of
sulfur-driven cooling (Pinto
et al
.,
1989
). Third, while they are geologically rapid,
LIP eruptions can still span a million years or more, potentially allowing the
climate system to recover from intermittent fluxes of relatively short-lived volcanic
gases such as SO
2
. Finally, each mass extinction is associated with a distinctive
pattern of environmental stress as recorded in the geological, geochemical and
palaeontological records (Knoll
et al
.,
2007
; Wignall,
2001
); these distinctive
patterns pose informative but challenging hurdles for any overarching model.
In recent years, volcanological understanding of LIP eruptions has grown more
nuanced. Abundant volcaniclastic deposits associated with the Ferrar, Emeishan
and Siberian Traps LIPs support episodes of phreatomagmatic and/or magmatic
explosivity (
Chapter 1
; Black
et al
.,
2011
; White
et al
.,
2009
; Wignall
et al
.,
2009
).
As detailed by Self
et al
.in
Chapter 11
, under certain conditions plumes from LIP
eruptions may intermittently breach the tropopause. Palaeomagnetic secular
variation studies (
Chapter 5
; Chenet
et al
.,
2009
; Chenet
et al
.,
2008
; Pavlov
et al
.,
2011
) and ultra-high-precision geochronology (Blackburn
et al
.,
2013
)
indicate that LIP magmatism often occurs in pulses, compressing gas emissions
into several concentrated convulsions.
Current research has focused on CO
2
release (Sobolev
et al
.,
2011
), sediment
degassing (Beerling
et al
.,
2007
; Ganino and Arndt,
2009
; Svensen
et al
.,
2009
),
acid rain (Campbell
et al
.,
1992
), ozone depletion (Beerling
et al
.,
2007
; Visscher
et al
.,
2004
) and shifts in continental weathering (Dessert
et al
.,
2003
; Schaller
et al
.,
2012
) as potential links between LIP magmatism and global environmental
change. Possible changes in ocean circulation from prolonged sulfur cooling
(Black
et al
.,
2012
; Miller
et al
.,
2012
) also warrant further investigation. In this
contribution we will employ the
252 Ma Siberian Traps as a test case. Where
possible, we will evaluate these proposed climate forcing mechanisms using a
global model of atmospheric chemistry and climate (Black
et al
.,
2014
; Kiehl and
Shields,
2005
), and we will compare the conditions of these simulations to those
expected for other Phanerozoic large igneous provinces.
~
20.2 The Siberian Traps: a case study
The Siberian Traps LIP constitutes a strong test case for the environmental effects
of LIP magmatism because of its unusual size, its continental setting and its
association with the catastrophic end-Permian mass extinction (Kamo
et al
.,
Siberian Traps is dif
cult to estimate due to erosion and uncertain intrusive
volumes, but has been estimated as
>
3,000,000 km
3
(Reichow
et al
.,
2009
).
Volcaniclastic rocks characterize the lowermost parts of the volcanic section in
