Geoscience Reference
In-Depth Information
C
HAPTER 11
ARE ALL MASS
EXTINCTIONS CAUSED
BY COLLISION?
All five major mass extinctions would turn out to have
been caused by the same mechanism, an asteroid collision.
1
Luis Alvarez
In
his 1983 talk at the National Academy
of
Sciences, Luis Alvarez
left
no
doubt just how far he thought his theory extended. He did
acknowledge that the prediction quoted in the epigraph had not yet
been confirmed, but made it clear that he believed it eventually
would be. If it were confirmed, then not only might the explanation
of mass extinctions have been discovered, so might the driving force
behind evolution itself. Though geology offers no Nobel prize, the
discovery of a robust general theory for mass extinctions, and espe-
cially of one linking them to extraterrestrial causes, surely would
rank as one of the great scientific accomplishments of the twentieth
century and place its authors in Nobel territory.
Physicists, even more than other scientists, seek the explanation
of more than individual phenomena—they want to uncover the
grand unified theory that will explain how each of the fundamental
physical forces arises and interacts. Einstein, for example, tried to
show that both electromagnetism and gravity derived from the same
fundamental "force field." He was unable to do so, nor has anyone
been able to since. Few geologists have even tried to imagine an all-
encompassing theory for the earth: What could the unifier possibly
be for the complex and seemingly random set of processes that char-
acterizes our planet? Yet, we must ask the question: What of impact?
It first created the inner planets through accretion, then destroyed
I
83
