The Final Confrontation - Four Revolutions in the Earth Sciences - page 108

Gondwanic continents, Africa, Antarctica, Australia, India and South America . . .
support the hypothesis of continental drift.” 17
By 1964, to the paleomagnetists, that the continents had drifted had become
an observational fact. If there had been a “confrontation,” Bucher and those who
agreed with him had already lost.
Bullardandhiscolleagueshaddecidedtouseacomputertotestjusthowgoodis
the fit between the continents facing across the Atlantic Ocean. Instead of match-
ing the continents at their coastlines, which are mere artifacts of current sea level,
they let the computer find the depth ofbest fit. It turned out to be at the 500-fathom
(about 3,000-foot) contour, “on the steep part of the continental edge.” 18 Bullard
and his coauthors plotted the results on a map that highlighted the gaps and over-
laps, finding that they are small and largely offset each other. Since the two con-
tinents had been apart for scores of millions of years, during which time erosion
and deposition must have modified their edges, the fit was better than even the
strongest proponent of drift could have wished: too good not to be true. Like the
map of the corrugated Atlantic floor, the “Bullard fit” made an indelible impres-
sion on the minds of geologists. For many, the map lit the way as they traveled the
path from regarding drift as impossible, to possible, to probable.