Geoscience Reference
In-Depth Information
Hutton: "The present is the key to the past." Catastrophism was
rejected; Lyell and subsequent geologists needed no "help from a
comet."
Of course, the slow processes that we see today at the earth's
surface—wind- and water-driven erosion and deposition, the ad-
vance and retreat of glaciers and the sea—can be projected back
into the past, and, in that sense, the present is at least a part of
the key to the past. Thus a case could be made for retaining the
uniformitarianism of process. But the whole edifice has caused such
damage, and is today so misleading, that the case for abandoning
uniformitarianism is much the stronger. Strict adherence to uni-
formitarianism clearly played a role in delaying for half a century the
recognition of continental drift and its modern version, plate tecton-
ics. As for meteorite impact, Marvin writes, that "Uniformitarian-
ism . . . probably has been the single most effective factor in pre-
venting geologists from accepting the idea ... as a process of any
importance in the evolution of the earth."
2
If we measure from the
date of Gilbert's erroneous conclusion about the origin of Meteor
Crater in 1891, to 1980, the year of the first Alvarez paper, unifor-
mitarianism and anticatastrophism cost geology nearly 90 years. But
continental drift and meteorite impact are arguably the two most
important processes that have affected the history of the earth. How
much value remains in a paradigm that helped to retard the recog-
nition of both for generations?
All scientists, geologists included, study cause and effect and
then project to cases where only effect can be seen. But that is all
that the uniformitarianism of process amounts to, and it is drastically
incomplete. Is there any longer a reason for geologists, alone among
all scientists, to give an exalted name to the standard modus operan-
di of science? Doing so is more apt to misdirect geologists of the
future, and to load them with the baggage of the past, than to assist
them in understanding the history of our planet.
Where do the traditional uniformitarian explanations of mass
extinction—changes in climate and sea level—stand today? Has ad-
ditional evidence been uncovered since the Alvarez theory appeared
in 1980 that lends them greater credence? No, just the opposite.
While the Alvarez theory has grown stronger, they have grown
weaker. I noted earlier that David Jablonski found that major mass
extinctions failed to correlate in any way with known changes in sea
level, global climate, and mountain building.
3
Recently, John Alroy
of the Smithsonian compared the appearance and extinction of
mammals with the ups and downs of global climate over the past
