Environmental Engineering Reference
In-Depth Information
20
Environmental effects of large igneous province
magmatism: a Siberian perspective
benjamin a. black, jean-fran¸ois lamarque, christine shields,
linda t. elkins-tanton and jeffrey t. kiehl
20.1 Introduction
Even relatively small volcanic eruptions can have signi
cant impacts on global
climate. The eruption of El Chichón in 1982 involved only 0.38 km
3
of magma
(Varekamp
et al
.,
1984
); the eruption of Mount Pinatubo in 1993 involved
3
-
5km
3
of magma (Westrich and Gerlach,
1992
). Both these eruptions produced
statistically signi
cant climate signals lasting months to years. Over Earth
'
s his-
tory, magmatism has occurred on vastly larger scales than those of the Pinatubo
and El Chichón eruptions. Super-eruptions often expel thousands of cubic kilo-
metres of material; large igneous provinces (LIPs) can encompass millions of cubic
kilometres of magma. The environmental impact of such extraordinarily large
volcanic events is controversial. In this work, we explore the unique aspects of
LIP eruptions (with particular attention to the Siberian Traps), and the signi
cance
of these traits for climate and atmospheric chemistry during eruptive episodes.
As de
nedbyBryanandErnst(
2008
), LIPs host voluminous (
>
100,000 km
3
)
intraplate magmatism where the majority of the magmas are emplaced during short
igneous pulses. The close temporal correlation between some LIP eruptions and mass
extinction events has been taken as evidence supporting a causal relationship
(Courtillot,
1994
; Rampino and Stothers,
1988
; Wignall,
2001
); as geochronological
data become increasingly precise, they have continued to indicate that this temporal
association may rise above the level of coincidence (Blackburn
et al
.,
2013
).
Several obstacles obscure the mechanisms that might link LIP magmatism with
the degree of global environmental change suf
cient to trigger mass extinction.
First, for Mount Pinatubo-style sulfur cooling, explosive eruption is crucial. The
radiative effects of sulfur aerosols are much greater when the aerosols reach the
stratosphere via explosive plumes (Robock,
2000
). Second, as the magnitude of
