Geoscience Reference
In-Depth Information
now covered with water, leaving the crater hidden under younger
sediments. It might have landed in the 20 percent of the seafloor
that has subducted (carried down beneath an overriding tectonic
plate) since K-T time. The crater might be buried under the polar
ice caps. It might have struck on land but now be so eroded as to be
undetectable, or it might be buried there beneath younger rocks. It
might have triggered a volcanic eruption and now be covered with
lava. Finding the crater thus would require more than good sci-
ence—it would require good luck.
FINDINGS
Locating the K-T impact crater obviously would provide the most
corroborative evidence of all, but prior to 1990, no crater of the
right age and size had been discovered. Indeed, the only candidate
much discussed was the buried structure at Manson, Iowa, but it
seemed too small to create a worldwide catastrophe and, some crit-
ics said, was a cryptoexplosion structure formed by underground gas
explosions, as Gilbert and Bucher had claimed for Meteor Crater.
(Chapter 7 is devoted to the search for the K-T impact crater.)
The six predictions just reviewed are specific to the Alvarez the-
ory, but there is a seventh prediction that can safely be made when-
ever a theory with far-reaching implications is explored.
PREDICTION 7:
Unanticipated discoveries will be made.
As theories are explored, unexpected discoveries almost always
turn up. Sometimes these surprising findings turn out to strengthen
a theory; sometimes they provide critical evidence that helps to fal-
sify it. With the advantage of 20-20 hindsight, one can often see
that a particular discovery could have been anticipated and stated
as a prediction.
FINDINGS
Prior to the Alvarez discovery, little was known about the clay layer,
but now a host of techniques were applied to it. Three scientists
from the University of Chicago made one of the most astonishing
finds.
1
1
Searching the Danish K-T clay for a possible meteoritic
noble gas component, they found large amounts of soot, which was
missing in the other late Cretaceous rocks and marine sediments
that they analyzed for comparison. If the clay layer had been
deposited suddenly, for which there is much independent evidence,
