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Title: Snowball Earth : The Story of the Great Global Catastrophe That Spawned Life as We Know It by Gabrielle Walker ISBN: 0-609-60973-4 Publisher: Crown Pub. Date: 18 March, 2003 Format: Hardcover Volumes: 1 List Price(USD): $24.95 |
Average Customer Rating: 3.93 (15 reviews)
Rating: 5
Summary: A gripping tale... can't wait to see the ending....
Comment: I honestly couldn't put this book down.
I'm a microbial ecologist, and I picked up the book looking for insights into the history of early life on earth. I had read the significant Science and Nature papers on the subject of Snowball earth, but this book was something else entirely. I nearly forgot about my interest in the subject matter and was enthralled by the characters that Walker brought to life.
Snowball Earth is a nice 'story', and I am eager to see how this theory plays out in the coming years. I like it as a working hypothesis for the moment, and I am intrigued by the proposed link between Snowball events and metazoan evolution. The timing seems right, but I don't think a compelling mechanism has really been put forth yet.
Walker does a thourough job on this topic, and I hope she writes more books!
Rating: 5
Summary: Easy read about scientific facts and speculations.
Comment: In this easy-to-read and sometimes entertaining book, Gabrielle Walker tells the story of the discovery of the massive glaciations of pre-Cambrian Earth that have come to be known as "Snowball Earth". The fact that "Snowball Earth" really happened is not controversial, despite what some reviewers have suggested. The basic reason is the well-known fact that the Sun is slowly getting hotter and was significantly less bright a billion years ago. Also not very controversial anymore are other assertions like the fact that the dinosaur extinction was indeed caused by the collision with Earth of one (or more) comets or asteroids. Walker is not uncritical about these facts, just well informed. There are some small misstatements in the book, like the assertion that magnetic pole inversion have happened regularly through geologic time, while, in fact, there was no inversion for an extended period (tens of millions of years) in the Mesozoic. More controversial, is the idea that "Snowball Earth" somehow "caused" the Cambrian animal radiation. This is the subject of just chapter 9. In many ways this is, for me, the most interesting chapter of the book, and also the most problematical. I assume that most of the experts don't doubt a relationship between the end of "Snowball Earth" and the "Big Bang" of animal life. But most would just assume that the big glaciations prevented the radiation of animals, that otherwise were ready to go, with Hox genes and all. Still chapter 9 is very interesting. Many of the discoveries discussed in it, like the finds of trace fossils of known Ediacaran "animals" have not been published in refereed journals. If it were true, Fedonkin's find of slug-like trails left by Kimberellas, would be extremely important. It would prove that this "animal" is indeed an animal, probably related to the common ancestors of mollusks and annelids. It is very strange that the Fedonkin has chosen to use Walker's book to announce such an epochal discovery. I think the explanation is in Gabrielle's picture, in the back of the book: she is so charming and enthusiastic that nobody can avoid bragging to her about their latest finds! My biggest complaint is that this book really needs graphs and pictures.
Rating: 4
Summary: Snowfights
Comment: It is always exciting to learn about new ideas on the cutting edge of any science. The idea of a Snowball Earth has sparked many debates and arguments. Snowball Earth, by Gabrielle Walker does more than defend the theory in face of academic scrutiny. She manages to introduce the reader to the man behind the theory, and in effect, write a story that resembles, the relationship between the man and his theoretical construct. This is what makes Snowball Earth, such a fascinating work. We are allowed to witness the man at his best, and at his worst. We are given an honest and open-minded view of the individual and his sometimes-sour relationships with others (generally those who do not follow his ideas). His arrogant and egotistical nature is not excused in any way, more fittingly it is used as a reason for his genius. The capacity to strongly trust what he believes in, makes Dr Paul Hoffman such a champion of his Snowball Earth Crusade, and more of the protagonist in the tale, than the theory itself.
The book opens with a chapter that accurately describes the manner in which Dr Hoffman approaches both life and his work. When still a young Postgraduate student with a passion for distance running, and on his very first attempt at the Boston Marathon, managed to come in a very respectable 9th place. His conviction to the cause, and self-will were the fuels which drove him on in the race, and remain to this day the fuels which drive his ambitions to prove to the world that the world has been through periods of massive freezing, the entire globe has been entirely frozen over, including the equatorial regions. This theory has been contested many times since it was first proposed to the Geological community, due to the fact that perhaps the most fundamental principle in Geology - Uniformitarianism, states that everything in the world behaves today as it always has. Processes, which are occurring today, have been occurring throughout Geological time. This means that we have the capacity to interpret past events through direct observation of present day functions. The idea of a Snowball Earth, then flies in the face of uniformitarianism.
Gabrielle Walker accurately describes the manner in which this affects the relationships between Dr Hoffman and his critics and compatriots. His driven belief in his own abilities (as proven by his Boston Marathon performance) often causes him to bash heads with those around him, not winning him many personal friends in support of his outlandish theory.
Critics of the snowball model (such as Nick Christie-Blick, Hoffman's chief adversary) insist that if at any time the entire surface of the earth was frozen over, the amount of insolation absorbed within the atmosphere, would greatly decrease, due to the nature of ice. The reflection of this radiation back into space would mean that ice depths would increase, and the earth would remain locked in a state of ice indefinitely. Dr Hoffman's Snowball Earth theory entails the periodic covering of the entire surface of the earth, under a layer of ice around 20km thick. This ice would then be thawed eventually after around 100 000 years or so due the combined action of volcanoes, and the releasing of gases such as CO2. These gases are released in the atmosphere, and they, along with the surface of the earth, absorb the incoming solar radiation and re-radiate it back down to the earth's surface. The net effect of this, is that enough internal heat is stored within the atmosphere to raise global temperatures, and in doing so, begin the melting process, which relieve the earth of its frozen blanket, to more closely resemble those conditions we know of today. The way, in which Walker describes complicated scientific processes, is simple and easy to follow, which is the mark of a good scientific biography.
Walker is giftedly able to place the reader in the company of Hoffman and his colleagues as they scour parts of the globe looking for evidence for rocks that would prove the earth had indeed frozen over entirely. We are taken from places as diverse as Svalbard Norway, to closer to home, Namibia. The signs and signatures of rocks that had been frozen are searched for. In order for Hoffman to prove the entire surface had indeed frozen, he needed evidence that showed that the rocks at the equator had frozen too. To do this he needed to identify the mark of rocks that had been frozen, then place them at the equator through the study of palaeomagnetism. When newly formed rock solidifies, it holds with it the magnetic signature of the Earth's magnetic field. By knowing the alignment of that field, you can work out the approximate latitude of that rock at formation. The work of Joe Kirschvink, enabled Hoffman to show that there had indeed been equator rock which at some stage had been frozen. The specific time period searched for by Hoffman was between 750-590 million years ago, the time before the Cambrian explosion. The reasons for this are made very clear by Walker, and explain the draw and attraction of the theory to the layman. Before this time, all life that existed on earth was in the form of a primordial sludge of single celled organisms. After the Cambrian explosion, the world entered a period of massive diversification, in which single celled organisms became multicellular life. We saw the birth of shells, and scales, and spines. Teeth and external and internal skeletal structures. The ancestors of life on earth as we know it today. This is why Dr Hoffman is so interested in finding these specifically aged rocks, with these specific palaeomagnetic signatures. Snowball Earth may then prove to be the catalyst that sparked the emergence of complex life on earth. The cooling and rapid warming of the earth may have created an environment stressful enough to cause single cells organisms to huddle together for survival. Creating specific functions for each cell, and uniting them to form a single complex entity.
The way in which Gabrielle Walker approaches the tropic is informed and passionate. Her capacity to convince the reader of the validity of the theory may even rival that of Dr Paul Hoffman himself. Snowball earth is a fascinating read, with massive contemporary appeal in the wake of modern existential reasoning. We may have found the source of complex life, floating in a glass of cool drink.
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