Walker: Snowball Earth

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Gabrielle Walker, Snowball Earth : The Story of the Great Global Catastrophe that Spawned Life as we Know it. New York : Crown Publishers, 2003. xiii + 269 pages.

Gabrielle Walker’s Snowball Earth is geology done right! She looks at one specific geological theory (and a somewhat controversial one that has detractors as well as supporters) and the main scientists behind it. It’s a combination mini-biography, travelogue (she goes to Australia, Nigeria, the Arctic, etc.), and interesting science!

The "Snowball Earth" theory suggests that at some point in the earth’s history, its surface was completely frozen. I’m not going to go into all of the details (because I had to return the book to the library), but the eventual thawing could have caused an important ‘outbreak’ of life! Walker is very talented at explaining things in a way that makes sense, without glossing over the important details and issues, and her descriptions are incredible (for a taste of her writing, check out my favorite passages below).

I found Snowball Earth compulsively readable: I read it all in a single sitting (it’s not a super-long book), wanting to find out what all of these interesting people were doing. I’d highly, highly recommend this one to everyone.

Favorite Passages

"Though sea ice is gray when it first forms, it whitens year by year as its brine drains back into the sea. Even gray young ice is often dusted with white snow. But a frozen ocean is far from monochrome. Gashes of open seawater, created as the pack ice is ripped apart by wind and weather, expose the deep turquoise roots of the floating sea ice. And the dark ocean reflects in the clouds, streaking them the color or a bruise. 'Water sky,' this is called, and polar sailors have long used it as a clue for where to point their ship next as they navigate perilously through the pack."


"Spend long enough in the Arctic, and you will develop your own definition of a bad fly day. According to Paul, a bad fly day is when you can hit your arm once and find a hundred corpses in your hand. On bad fly days, mosquitoes whir and whine around your head in a dense claustrophobic cloud. Blackflies crawl everywhere on your clothes and skin, and into every crevice. To avoid inhaling them, you have to breathe through your teeth. If you run your hand through your hair, it comes back greasy and bloody. At the end of a bad fly day, you empty your pockets of globs of dead and half-dead flies. They have crept up your wrist, down your neck, under your belt, down the tops of your boots. On bad fly days, you soak yourself with industrial strength Repex, the repellent of choice. Repex doesn’t keep the flies way, but it stops them from biting. It lasts two or three hours. On bad fly days you don’t have to be reminded to reapply. In the Canadian Arctic, between the fine few weeks of June and the return of winter in late August, every day that is not freezing cold or blasted with wind is a bad fly day."


"Relationships among geologists are intense. By its nature, geology involves traveling with your colleagues to remote places, working long, hard hours in sparse conditions, living on top of one another and away from other people for weeks on end, having little contact with the outside world. Think of submarine crews, or Antarctic explorers. Think of throwing obsessive, opinionated people together in places that they can’t easily leave. Their personalities become magnified. They bond or they break."


"One party-goer, peering over his shoulders, asked if [the bacteria] liked beer. Joe promptly applied a drop of Foster’s lager to one side of the breaker, and then flipped the magnet to make that side 'south.' The bacteria galloped toward the spreading yellow liquid, but as soon as they tasted it, they turned tail. Australian bacteria apparently do not like beer. Later, Joe tested the northern bacteria in his hometown of Phoenix, Arizona. The American bacteria showed no inclination to turn tail at the Foster’s-water interface. They swam directly into the beer, and promptly perished. 'They died happy,' says Joe. American bacteria, unlike Australian, had no idea when to call it a day."


"Paul wound his way hurriedly down the canyon on the sandy river floor, dodging the rocks and branches swept there by an old flash flood. Up ahead his lights picked out a thick black log, maybe nine feet long, lying in the sand. The Toyota could handle that, no problem. But at the last minute Paul swerved around it, striking what might have been a glancing blow. The log had seemed to twitch as he passed.

"He was intrigued. He slowly backed up, craning his neck to see the scene illuminated by his white taillights. The log had vanished. No, it was standing up, and heading toward the vehicle, fast. It was chest high, four a half feet above the ground, just about the height of the Toyota’s open window. Now Paul could see that it had curious yellow rings the length of its body. It was a zebra snake, a western barred spitting cobra. It had spread its black hood angrily around its face and it looked unnervingly in the wing mirror. Paul remembers wanting to laugh. This was like the T. rex scene that appeared in Jurassic Park, reflected above a warning that 'Objects in mirror are closer than they appear.'

"But he also knew that zebra snakes were deadly. The toxin would quickly paralyze his muscles, and shut down his breathing. He had no serum as an antidote, since serum has to be kept cool and Paul had no refrigerator. Without immediate artificial respiration, he would suffocate. If someone pumped his lungs with their own air constantly while he was rushed back along these twisting canyons, in the dark, out along the bush tracks to the nearest village and then on and on to a town that perhaps had a hospital, he might survive without too much brain damage. Zebra snakes don’t even need to bite you. They are called spitting cobras for a reason. Normally they’re excessively shy, but when aroused they can spit their cytotoxic venom six feet or more. This one was clearly aroused, and Paul hastily rolled up his window.

"The snake book in the passenger door of Paul’s Toyota contains many lurid pictures. Alongside the featured snakes from southern Africa, you can see the human effects of their venom: rotten arms, legs and hands, attached to bodies with pained, hopeless faces; limbs and torsos with puncture points surrounded by skin that is black, blue, yellow, swollen, pitted and blotched. 'Don’t read the snake book,' Paul says to every newcomer, to first-time field workers and naive young graduate students. 'It will only give you nightmares.' Everybody immediately opens the book and stares.

"You are told, when you first come to Namibia, never to unroll your sleeping bag until the very last minute, just before you climb in. Each morning, when you wriggle out of the bag, you immediately bind it into a tight bundle. Everybody knows about the sleeping bag unrolled at Khorixas rest camp by an unwary student, about the zebra snake that slid inside during the day and was there waiting for him when he retired to his tent. He survived, just, since he was relatively close to town. When you’re camping out in the remoter parts of the Namibian desert, you don’t need to hear this story twice."

-- Notes by EVA

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