Geoscience Reference
In-Depth Information
FIVE
EUREKA
When Paul Hoffman became obsessed with the Namibian ice rocks, he sensed they would eventually
reveal to him some important story about the history of the Earth. Throughout the 1990s, he returned
every year to study them. He was where he wanted to be, driven by a new mission, as happy now in
Africa as he'd ever been in the Canadian Arctic.
Each season he went eagerly from outcrop to outcrop, making every moment of his precious field
time count. There was no such thing as a rest day. Any days not spent on the outcrops were for driving
between them. Paul would often hike up and down hills, over rocks and down stream cuts and gullies.
He went out fast and hard. He would work his way up through the sequence, noting what type of rock
was there, how the rock formed, whether it came from a delta, a river, a deep ocean floor, how it related
to the rocks above and below. He would put a sheet of clear Mylar over an aerial photograph and draw
in the rock type with a sharp pencil. Sometimes he stopped to measure the rocks in a particular section.
He took out a folding carpenter's ruler and climbed up the section, recording its thickness yard by yard,
noting any peculiarities in his waterproof yellow notebook (waterproof to prevent the figures smudging
from sweat—there's no rainfall in the Namibian desert during the dry season). He developed his own
shorthand of neat hieroglyphs for sandstone and mudstone, diamictite and carbonate, and the sharpness
of the contacts between them.
This was standard field geology. The first task in a new field site is always to build up a detailed
picture of the whole geological terrain. Nothing geologists discover holds any weight amongst their col-
leagues unless they fully understand, and can describe, the context in which it is found.
Sometimes Paul collected samples. He would take a geological hammer and smash chunks off the
rock face. There's something about holding a geological hammer that makes you want to hit rocks.
Weigh one in your hand, and you'll find yourself itching to whack something with it. Still, to carve a
hand sample into just the right shape for your pocket requires considerable skill. Paul is very, very good
at it. If his geology career went awry, he could make a living as an ornamental rock chipper.
Perhaps he wants a sample of a particular structure in the rock, or something that shows exactly how
the contact looks between two different rock types. He holds an unwieldy chunk of rock in one hand and
chips away at it casually. Thwack, smack, smack, and all the useless bits miraculously fall off, all the
right bits stay behind. The trick apparently lies in choosing the right sample, finding the flaws that will
dictate where the rock breaks, and then hitting it at the right angle in the right place, with just the right
amount of force. When there's anyone around and a sample to be had, Paul can't resist showing off his
skills. It's infuriating to watch him. Also oddly inspiring. You want to rush off furtively and practise.
You want to do it as well as he does.
Every day Paul would stay out on the outcrops as long as he could—too long sometimes. He often
had to race back to camp before the heavy Namibian night fell. The surface of the rocks was rough, like
sandpaper. If he tumbled on them in the darkness, his skin would be shredded. The nights were cold as
well as dark. Paul's field season spanned the Namibian winter, when the days were still hot, but evening
