Geoscience Reference
In-Depth Information
It's the Data
Why did scientists reject the four theories discussed in this topic for so long, only
tohavelatergenerationscometoregardthemasvirtuallyself-evident?Theanswer
is now plain: scientists accepted the theories when the data demanded that they do
so. To call themselves scientists, they had no choice.
But at first the data were missing or open to different interpretations. Kelvin's
calculations of the age of the Earth depended not on data but on Fourier's mathem-
atics and Kelvin's assumption that the Earth was born molten and has no unknown
source of heat. The data of the hourglass calculators on sedimentation rates and
sediment accumulations were so imprecise and malleable that their results were
virtually worthless. Then came the measurement of the amounts of parent-daugh-
ter pairs in minerals, and soon there was no denying that the Earth is billions of
years old.
Wegenerpresentedenoughgeologicalevidencetoearncontinentaldrifttheright
to stand as a working hypothesis, but that evidence was qualitative rather than
quantitative, and geologists could choose to interpret it differently. Then came the
flood of hard geophysical data in the wake of World War II. The convergence
of many lines of quantitative evidence, especially the data from paleomagnetism,
showed that tectonic plates move and carry continents piggyback.
Until the data from the space age arrived, scientists could claim without fear of
contradiction that the craters of the Moon are volcanic. As to terrestrial craters,
they were few, obscure, and again open to different interpretations. Then came
the photographic evidence that meteorite impact had caused the countless lunar
craters. Shatter cones, coesite, and careful geological mapping showed that Meteor
Crater and other terrestrial cryptovolcanic structures also derive from impact.
Geologists have found nearly two hundred terrestrial craters by now, and those
must be only a fraction of the number that have formed on Earth over geologic
time.
The possibility that the K-T boundary derives from meteorite impact made it the
most studied geological interface. As a result, a mountain of geochemical and geo-
logical data so well corroborate the Alvarez theory of dinosaur extinction that to
dislodge it will take convincing, noncoincidental evidence on the other side.
