Geoscience Reference
In-Depth Information
and leapt backwards. “Nick! The sheep's alive!” Damn, damn, damn. Not the way to impress your
brand-new adviser, before you've even made it into your first semester.
Nick was unfazed. He bought her a tent, a lantern, a set of pans. He took her to various possible
research sites in the Flinders Ranges. He helped her to choose which rocks she wanted to work on for
her Ph.D., showed her how to hook up the radio, and left her there.
At first the silence was the worst. Then the unexplained bumps in the night. Kangaroos would hop
silently by until they hit a gravelly streambed and suddenly wake her with their crash. Reclusive emus
would come out at night to skitter on the stream pebbles, left, right, left, right, like people running.
Once there really were people, whooping their way along a remote bush track, shining bright search-
lights and firing guns. The air was full of bullets and agonized screams. Linda stayed in her tent. Later
she discovered it was part of an authorized cull of the feral alien animals, the cats and foxes that be-
devil the Outback.
But for the most part the Outback turned out to be benign and beautiful. For annoyance value,
there were just the idiotic galahs, brightly coloured parrots that would periodically launch themselves
en masse from a tree, shrieking wildly and divebombing the site. And the bugling cockatoos, and the
oversized Australian magpie, actually a relative of the crow, but with an enchanting, lyrical warble
that echoed hauntingly among the gum trees, and almost made up for the rest. The birds were useful in
a way. No need for an alarm clock when you have an ear-shattering dawn chorus every morning, 6:45
sharp.
Linda had never intended to test the Snowball idea. She was supposed to be studying some car-
bonate rocks that had formed long before the ice. But, having worked among the ice rocks for the past
two years, she couldn't help being intrigued by them. She'd heard about Joe Kirschvink's magnetic
work and the more detailed studies by George Williams. And she decided to see whether she too could
detect the faint magnetic traces in the rocks.
A few weeks into her 1995 trip, Nick came out to help. He hadn't encouraged Linda to work on
the ancient ice, but he was curious to know how her results would turn out. Nick, the details man, was
always pestering and probing. In the field he could drive you mad. He doesn't—ever—let something
lie. As he and Linda drilled and washed and carried samples back and forth, he asked her incessantly
about the precision of her magnetic measurement. To Linda, it simply wasn't the most important issue.
Details often matter, but that particular detail would come out in the wash. But Nick was consumed by
it. A few weeks after he left to return to his own field site, Linda went into the small town of Hooker
to collect her mail, sent to her care of “general delivery”. Among her letters was one from Nick, via
his field camp several hundred miles to the north. The page was covered with careful diagrams and a
detailed analysis of the factors affecting the precision of Linda's measurements. He just couldn't let it
go.
At the end of the season, Linda headed back to New York to analyse her samples. The work was
exhausting and painstaking. The magnetics machine was already booked up for the days and evenings,
so she worked on it through the nights for six weeks. But in the end she hit pay dirt. Though all the
rocks she collected had looked more or less the same, pale and reddish from the magnetic minerals
they contained, some of them had a field pointing northwest, and in others the field was southeast. To
Linda, that meant only one thing. These ice rocks contained a record of ancient magnetic reversals.
A magnetic reversal occurs when the Earth's magnetic field spontaneously swaps directions, so
that magnetic north becomes magnetic south. Our planet's magnetic field is generated by molten iron
sloshing around in the Earth's core, and the flipping must somehow be related to changes in this deep,
hot liquid. But the details remain a mystery. What we do know is that this bizarre event takes place
