There have been six major (and many
minor) extinction events on earth during the past 510 million years.
Scientists have put forth many
explanations for these extinction events. At present, there is no conclusive
agreement about the cause of any one of these events, much less all of the
extinction events. Scientists can't even agree on the events, themselves (i.e.
Was the Triassic extinction event really an extinction event?).
A summary of the major extinction
events and the most accepted proposed causes is as follows:1
1. Cambrian Extinction510 MYA
a. Glacial
Cooling b. Oxygen Depletion
2. Ordovician Extinction440
MYA (50% of all animal families go extinct)
a.
Glaciation and Sea Level Lowering
3. Devonian Extinction365 MYA
(30% of all animal families go extinct)
a.
Glaciation b. Meteorite Impact
4. Permian Extinction250 MYA
(60% of all animal families go extinct)
a. The
Formation of Pangaea b. Glaciation c. Volcanic Eruptions
5. Triassic Extinction202 MYA
(35% of all animal families go extinct)
a. Fluctuating Sea Levels
b. Bolide Impact c. Volcanic Eruptions d. Possibility there wasn't
a mass extinction
6. End-Cretaceous Extinction65
MYA (50% of all animal families go extinct)
a. Meteorite Impact b.
Volcanic Eruptions
ONE STOP SHOPPING
This book proposes the idea that all of
these major extinction events (and many of the minor ones), stem from just one
cause: The natural kinetic effects of a cosmic impact on the planet Earth.
Certainly, it is not new to propose
that cosmic impacts have had a devastating effect on the planet earth.
In the 1980s, Louis and Walter Alvarez
found large amounts of iridium (which is only present on earth in significant
amounts via impacts from outer space) at the black ash layer which separates
the Cretaceous era from the Tertiary, 65 MYA (the K-T boundary). This
relatively large presence of iridium led them to propose that a large meteorite
impact had caused the End-Cretaceous extinction.
A few years later, an analysis of oil
exploration maps made by mapping magnetic anomalies showed an overgrown and
eroded impact site at Chicxulub in the Yucatan peninsula of Mexico. The site
dated to 65 MYA. Furthermore, in other excavated sites of 65 MYA, the
concentrations of iridium at the at the K-T boundary and the amount of ash at
that boundary generally increased as the explored
site was located nearer to the Chicxulub impact location.
With this confirmation of the "smoking
gun" (the Chicxulub crater), many scientists have accepted the idea that a
meteorite impact was the cause of the End-Cretaceous extinction. Furthermore,
many scientists have looked to cosmic impacts to explain other extinction
events.
However, the great majority of these
scientists have focused on the effects at the impact site, itself. While these
impact site effects would have considerable, I do not believe that these
effects would have been sufficient to cause the major extinction events.
Neither do several other scientists, each with their own set of reasons.
I believe that it was the effects at
the antipode (the exact opposite side of the earth), resulting in devastating
and sustained volcanism, that were the primary cause of the major extinction
events.
As David Charles Weber notes in a paper
published on 3/28/10, writing about the effects of the devastation caused at
the impact site of the Chicxulub crater:
"This would cool the earth to
create continuous killing frosts in the upper latitudes for as long as 10 years
and droughts in the tropics. But, this degree of sun blotting from a localized
explosion from the meteor impact would not have killed all of the plants near
the equator, even with the cooling and the drought. So, this doesn't explain
the complete eradication of the dinosaurs, which would have survived near the
equator and then repopulated the earth." 14
But, thousands of years of worldwide
volcanic winter caused by massive, aggressive and persistent volcanic action at
the antipode of the impact would explain the complete destruction of the dinosaurs ... especially if this large
volcanic hotspot was located at the edge of the moving continent, so that
water-laden crust could be subducted into the volcanic system, causing steam
and explosive results (see Appendix VII). |