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.
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.
"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
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
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
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