CHAPTER 3.2
FLOOD BASALT ERUPTIONS & MASS
EXTINCTIONS
An article in "Elements" in Dec. 2005 entitled
"the Link between Large Igneous Province Eruptions and Mass Extinctions" by
Paul Wignall asserts the following:
"In the past 300 million years, there has been a
near-perfect association between extinction events and the eruption of large
igneous provinces, but proving the nature of the causal links is far from
resolved." 77
He further states:
"The associated environmental changes often
include global warming and the development of widespread oxygen-poor conditions
in the oceans."
However, he also notes that younger volcanic
provinces have not led to high extinction rates. In other words, there is not a
mechanism to explain why it happens and why it doesn't happen.
77
An article by Steve Self and Michael Rampino published by
The Geological Society, July, 2010, lists a comparison of major flood basalt
flows and major extinctions. 76
They suggest that there is
likely to be a causal link between the creation of large igneous provinces and
mass extinctions. However, they note that finding the mechanism is quite
difficult. They say:
"Every now and again in geology, as in any other
science, evidence is obtained and presented that cannot easily be explained in
terms of familiar processes or accepted ideas. Such a case was continental
drift, proposed by Wegener in 1912, which languished as a theory for about 45
years because there was no logical explanation of HOW continents could move."
76 pg3
They go on to note:
"The time relationship between flood basalt
province formation and mass extinctions of organisms is another scientific
'hard nut to crack.'" 76 pg 3
When it comes to a
causal link between flood basalt events and mass extinctions, Rampino and Self
suggest that it may have to do with the gasses released. But they note that
basaltic eruptions are not particularly explosive, even though they are "often
very rich in dissolved sulphur, and sulphuric acid aerosols formed from sulphur
volatiles (largely SO2) are injected into the stratosphere by convective plumes
rising above volcanic vents and fissures." 76 pg 4
They also
remind us that some scientists suggest "that a coincidence of both a large
impact and a flood basalt eruption might be necessary in causing severe mass
extinctions." 76 pg 4
Clearly, this information tells us
that scientists are looking at Large Igneous Provinces (LIPs) and mass
extinctions. Some are also expressing the need for a coincidental large impact.
Until now, no one has presented a mechanism whereby large impacts cause
LIPs (and possible continental uplift) at the antipode, with directional
motion. If the LIP is part of an uplifted continent and if the LIP is at the
edge of the continent, then subduction can occur at the edge of the LIP.
Furthermore, much of this subduction will include water-infused crust that will
go into the lower reaches of the LIP. As the water turns to steam during
subduction, the nature of the eruption will change from gentle to violent.
These violent and persistent eruptions will provide plenty of explosive
sulfuric gases and ash.
In any case that I have investigated where a
continent was uplifted, there was at least a minor mass extinction, with the
exception of South America. However; with South America,
1. We had a major Oceanic Anoxic Event (OAE).
2. We had an antipodal hotspot that was interior to the continent's
edge, thus greatly reducing the opportunity for subduction of water-laden
crust.
3. We had a LIP that was moving in a straight line with the
continent in front of it, thereby not creating a situation where water-laden
crust could be subducted under it as the continent turned. Therefore, there was
little opportunity for explosive eruption.
The CAMP eruption
was huge and likely led to many situations where water-laden crust was
subducted into the path of basaltic eruptions. And, again, the ultimate cause
of the CAMP was the secondary effects of a very big impact.
Therefore,
I would argue that we now do have the mechanisms needed to understand the
causal relationships between LIPs and mass extinctions. Furthermore, I would
argue that the causal relationships necessarily involve very large impacts, as
well.
Self and Rampino include two charts showing correlative examples
of LIPs and mass extinctions. They suggest that more work be done in
researching this. 76 I would suggest that a chart of large impacts
be added to this correlative research. 77, 77, 76, 76 pg3, 76 pg 3, 76 pg
4, 76 pg 4
CLUES FOR THE FIRST MAJOR
EXTINCTION
In this book I have
refrained from trying to figure out anything older than the Permian extinction,
caused by a large cosmic impact around 252 MYA. The continuous tectonic
movement of the plates makes it very difficult to understand the influence of
impacts that occurred at dates earlier than that.
However, LIPs have an
advantage here. If they can be dated, they can be lined up with extinctions,
even if the underlying impact cannot be figured out. With impacts that are very
old, the evidence may be eroded, subducted or changed in form (i.e. it may get
folded into a newer mountain range, etc.).
Published in the journal
Geology in 2014, Dr. Fred Jourdan was able to show that the massive eruptions
in the Kalkarindji volcanic province in Australia ocurred 510 MYA, at the same
time as the first Cambrian mass extinction, which wiped out 50% of existing
species at that time. Another piece of the puzzle comes into focus.
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