Geoscience Reference
In-Depth Information
And to some of the people listening to Paul's lectures and seminars, the Snowball was going too
far. How could the Earth possibly behave in such an extreme way? He wants oceans that freeze over
completely, even in the tropics and at the equator. An ice age that lasted for millions of years. A planet
that then plunged from the coldest temperatures it had ever experienced into an intense hothouse with-
in just a few centuries. Carbon dioxide levels hundreds of times higher than have ever been seen in the
geological record. Rock weathering rates like nothing on Earth today. How could anyone ever accept
a theory that was so far out of the box?
The more Paul pushed, the more vehement many of his critics became. Particularly a certain geo-
logist from New York called Nick Christie-Blick.
N
AMIBIA
, J
UNE 1999
A
FLEET
of trucks swept off the concrete forecourt of the Safari Hotel in Windhoek and began the long
trek north. This was phase two of Paul Hoffman's Snowball mission. After his intensive programme
of lectures, seminars and presentations, he now brought a selection of his peers out to Namibia to
see the Snowball rocks for themselves. Among them was Nick Christie-Blick, a professor of geology
at Columbia University's Lamont Doherty Earth Observatory. Nick was unsympathetic to the Snow-
ball, annoyed by Paul's combative style and dismayed by the implication that the Earth had behaved
quite differently in the past. When Paul invited Nick on the field trip, he expected a certain amount of
trouble. “I knew Nick would be a pain in the ass,” he told me later, “because he always is.” What Paul
didn't realize was that the field trip was about to turn Nick into the Snowball's Chief Unbeliever.
Geology is an intensely personal science. It's not enough to study a sample of rock that someone
has carried home, or even to see photographs that they've taken. In this mind-twisting game of con-
structing a three-dimensional jigsaw from rocks that have been bent, thrust over one another, eroded
away or buried, the context can be everything. Show me just how sharp the contact is between the two
rock types on the outcrop, and how far it extends before it disappears from view. Where exactly in
the cliff face did these measurements come from? How accurate are your sketches? How detailed are
your maps? Geologists usually trust their own field data completely, but are much more reluctant to
place reliance on data from places they've never seen for themselves. Plate tectonics pioneer William
Menard put it well: “Some earth scientists believe in God,” he said, “and some in Country, but all be-
lieve that their own field observations are without equal, and they adjust other data to fit them.”
10
That's why field trips make up an important part of how geology is done. You do the field
work
on
your own, or with your few closest collaborators, for month after lonely month of mapping, sampling,
walking out contacts. When you're back home again, you might write a scientific paper describing
what you've seen and adding whatever interpretation you see fit. But the real test comes when you
take your colleagues out to look at the outcrops you've been working on, so they can judge the rocks
for themselves.
So Paul had brought along experts in Precambrian geology from around the globe. He had ar-
ranged everything, even paid for the trip out of his own precious grant money. This, he felt, was the
one way to convince his fellow geologists that the fledgling Snowball theory was sound.
Yet Nick Christie-Blick grew more antagonistic every day. Nick, like Paul, is a field geologist. He
patrols the world's rock surfaces for a living, measuring and probing and hammering his way through
millions of years of history. He lives in the United States, but is thoroughly British. He drinks tea,
speaks softly with a clipped Home Counties accent, and has the peculiarly English habit of carefully
