Geology Reference
In-Depth Information
In retrospect, some of the evidence against vertical tectonics should have been obvious.
As tall as the Rocky Mountains stand today, they are dwarfed by the seven-mile height of
Mount Everest and the mighty Himalayan range. Likewise, in contrast to the two-mile av-
erage depth of the oceans, Earth's deepest ocean trench, located off the Mariana Islands in
the South Pacific, plunges to an astonishing seven miles. Such topographic extremes could
not possibly be sustained in an isostatic world. Vertical tectonics couldn't be the whole
story.
Subtlehintsoflateraltectonics—theroleofsidewaysmotionsinEarth'sgeologicalevol-
ution—camewiththefirstaccuratemapsoftheNewWorld'scoastline.Bytheearly1600s,
the striking conformity between the eastern coastline of the Americas and the western
shores of Europe and Africa was plain to see. The same sinuous shape, the same embay-
ments and bumps, the rounded contours of extreme southwestern Africa and the match-
ing suggestive eastward curl of South America's tip—all pointed to some ancient jigsaw-
puzzle-like fit.
Several bizarre hypotheses attempted to explain the tantalizing transatlantic continental
match.AstronomerWilliamHenryPickeringofHarvardUniversity,whosupportedGeorge
Darwin's theory of fission origin of the Moon (as a molten blob hurled into space from
a rapidly spinning Earth), posited that simultaneously as the Moon was ripped from the
Pacific Ocean, on the opposite side of Earth the Atlantic Ocean opened wide. Others saw
the hand of God in the great Atlantic
S
. Perhaps the Atlantic coastlines were the shores
of Noah's mighty flood, which had been unleashed a few thousand years ago to create the
great ocean and “divide the lands.”
Systematic geological surveys might have helped resolve the question, but four hundred
years ago geology had not even been named, much less pursued in any systematic way.
Mining and agriculture, the driving economic forces behind the earliest geological surveys
ofthelateeighteenth century,werestrictly stateandnational affairs.Little effortwasmade
to match up geological formations across political boundaries; nor were the riches of one
principality seen as linked in any coherent way to those of any other. Gold was quite lit-
erally where you found it. In such a nationalistic mapping milieu, matching up geological
features across the great expanse of the Atlantic Ocean was hardly a priority.
The first detailed transatlantic geological comparisons were undertaken by an unlikely
scholar, meteorologist Alfred Wegener, who spent much of his career in the Arctic. (He
died at age fifty during a heroic winter rescue mission on the frigid Greenland ice sheet.)
Though his professional life was devoted primarily to studying the origins of weather, his
mostmemorableandlastingworkrelatedtowhathecalled“continentaldrift,”anearlyand
much disparaged contribution to lateral tectonics. The inspiration for this odd geological
digression came during World War I, when he served as a reserve lieutenant in the German
