Snowball Earth: The Story of the Great Global Catastrophe That Spawned Life as We Know It Hardcover – 1 Mar 2003
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Author, Gabrielle Walker earned her Ph.D. in chemistry at Cambridge University and spent seven years as a features editor at "New Scientist." The latter experience definitely had a hand in molding her breezy, yet clear and conscientious style. She follows her intrepid geologists to the ends of the Earth like an eager cub reporter in some 1930s B-movie, peppering them with questions, almost getting trampled by an African elephant in the Namibian bush, beset by freezing fog in the Kalahari Desert, clambering down the windswept, godforsaken rocks of Mistaken Point in Newfoundland.
This book is a combination travel guide to some of the least habitable places on earth, biographical sketches of the scientists who developed and tested the 'Snowball Earth' theory, and an introduction to the painstaking science behind the newest, most audacious 'deep time' history of our planet.
Before we get to 'Snowball Earth,' let me give you a flavor of Walker's running travelogue. Here she is speaking of Mistaken Point: "Nobody could love these barren lands, not even their mother. They are dreary and damp, their plants the color of overcooked spinach and rusty nails; when the wind is not buffeting them or rain beating them down, they are shrouded in fog. The pale, thin caribou wander over them like lost souls."
Now, on to the theory as expounded by this book. Several times in the history of Earth, most recently 700 million years ago, our planet froze completely over, possibly because all of the continents had migrated close to the Equator. This deep-freeze may have ended the multi-billion-year reign of single-cell slime and given a kick-start to the Cambrian explosion of complex life. Snowball Earth was finally melted by a build-up of carbon dioxide in the atmosphere, courtesy of volcanic eruptions which turned our planet into a hellish, hurricane-ripped green-house. Eventually the excess carbon dioxide was absorbed back into the oceans and the planetary crust. Multi-cellular life reveled in the first decent climate it had ever experienced, not realizing that meteor strikes and volcanic eruptions would occasionally wipe out up to 90% of its evolved species.
Could we get a repeat of Snowball Earth? Sure. As a matter of fact, the continents seem to be sliding toward the Equator again, which will allow ice to build up at the Poles and advance toward Earth's bulging midline. Will this happen during our lifetime? Nah. As Gabrielle Walker so vividly expresses it, the continental plates move at roughly the same speed our fingernails grow.
The geologists, paleontologists, and their science form the core of this marvelously written book. Walker does a meticulous job of relating both the scientific and the human side of the 'Snowball Earth' controversy. Her incisive portraits of the scientific movers and shakers, most especially the fiercely competitive Paul Hoffman, will stick in your mind long after you forget about drop stones, tidal rhythmites, and magnetic reversals in the Flinders ice rocks.
The snowball Earth theory is not entirely new, but the book is largely the story of Paul Hoffman, a brilliant, driven geologist who was eager to make some sort of difference in his field. Argumentative, energetic, and brilliant, he has a strong reputation as a geologist and as a difficult character. Disputes by him are not objective quibbles published in obscure journals, but stand-up, screaming fights. Partially because Hoffman has taken up a sort of gladiatorial grandstanding for the theory (he has made his own contributions and confirmations), there are equally adamant anti-snowballers. The combative nature of science is on display here; Walker writes, "Science works at its best when somebody puts forward a theory and everyone else tries to pull it down." She is good at describing the pains of field work (something at which Hoffman is adept), but academic battles are the emphasis in her book. Of course Hoffman hopes his ideas share the same fate as those of Alfred Wegener, whose ideas about Plate Tectonics were originally ridiculed; so far, they have survived the challenges about which Walker reports.
Particularly valuable in the theory is the light it might throw on the bloom of life into complex multicellular creatures. Of course a deep freeze would have been disastrous for all the simple slimes that were found all over the Earth when the freeze came. There might have escaped, however, pockets of cells that, according to the theory, were the precursors for the famous Cambrian explosion in the trilobite times. Perhaps the snowball produced the complexity, although this is far from clear. It is one of the many details that is going to have to be argued over. Walker winds up with a description of the Earth's future; if we are still around in a few hundred million years, we might well have to deal with a return of the snowball. It is too hard to think about time lengths of such spans, but geologists routinely do so, although the spans are back in the past. Walker's book is a good introduction to serious thought about such times, and to the very human way such science is done.