Environmental Engineering Reference
In-Depth Information
11
flood basalt eruptions:
understanding the potential environmental effects
Volatile release from
stephen self, lori s. glaze, anja schmidt and tamsin a. mather
11.1 Introduction
Continental
flood basalt (CFB) eruptions were huge lava-producing events that dwarf
the rates of basaltic volcanism today. Fire-fountaining explosive activity accompanied
these eruptions (Brown
et al
.,
2014
;seealso
Chapter 1
), and a series of such eruptions
leads to the formation of a CFB province. Research summarized by Courtillot and
Renne (
2003
) suggests that during the formation of some CFB provinces (e.g. the
Columbia River Basalt Group (CRBG),
Figure 11.1a
) the climax of volcanism, in terms
of erupted lava volume, can be brief, often much less than 1 million years in duration.
There is an intriguing age correlation between at least
five CFB provinces emplaced
in the past 300 Myr with mass extinction events and other environmental changes
(Wignall,
2001
; Courtillot and Renne,
2003
; Kelley,
2007
). The link between CFB
volcanism, extinctions and environmental change is thought to be due to eruptive gas
release from the magmas leading, amongst other processes, to atmospheric aerosol
formation and its radiative and depositional effects (see also
Chapters 13
,
14
and
20
).
Perhaps most striking is the age correlation of the emplacement of the Siberian Traps,
the largest-volume CFB province, with the greatest loss of
floral and faunal diversity
in Earth
'
s history (the end-Permian mass extinction,
252 Ma), with CFB volcanism
proposed as a trigger for this event (e.g. Wignall,
2001
; Reichow
et al
.,
2009
).
However, the mechanisms leading to the association between CFB volcanism and
extinctions have yet to be robustly and qualitatively demonstrated.
In this chapter we discuss two aspects of the relationship between CFB volcanism
and the potential, detrimental environmental effects it causes. These are (1) the
heights of volcanic plumes from CFB episodes, and (2) the emplacement timescales
and volatile release rates of CFB eruptions (we focus on volatiles released directly
from erupted magma). These are important source parameters for atmospheric
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