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As plate tectonics was being developed in the 1960's, the Apollo program and spacecraft were revealing the ubiquitous planetary cratering that would lead to a second revolution in geology: recognition that impacts by asteroids and comets have helped shape Earth's surface and the evolution of life. However, as Walter Alvarez contends in his slim book "T. Rex and the Crater of Doom," the excitement of plate tectonics distracted most geologists from paying attention to the lessons from space. Not until 1980, when Alvarez, his father, and some colleagues published their paper proposing an extraterrestrial cause for the Cretaceous-Tertiary mass extinctions were geologists forced to confront cosmic catastrophism.
It has been a painful conversion for most geoscientists, because impacts were considered to be antithetical to the uniformitarian dogma that dominated geology for two centuries. Heated debates in the 1980's over the Alvarez hypothesis is a tale not fully told in this book, despite the dust jacket's promise that it recounts "intense public debate, [and] friendships made or lost...." Although he writes of friendships made during field trips in distant lands, Alvarez is too civil to delve deeply into the rivalries, media mistakes, public antagonisms, or friendships lost.
"T. rex" has a simpler, yet fascinating story to tell. It is how Alvarez's geological career led him to study the K-T boundary layer at Gubbio, Italy, and how the immense Chicxulub crater was located, which proved his father's idea that global dust from an impact led to the holocaust 65 million years ago. The tale is personal, well written, and delightful. Alvarez also reflects on the history and philosophy of geology, making this book well suited for beginning geology students and literate non- geologists interested in how geologists think.
Alvarez portrays a modern geology, which builds on the interdisciplinary resources of physics, chemistry, and astronomy to fashion a synthesis about how our planet has evolved. Discovery of the famous iridium anomaly appears halfway through the book, beginning the mystery story about the hunt for the crater of doom. Although he gives credit where credit is due, this is primarily the story of Walter Alvarez's own quest for the answer, involving both miscues and successes, finally focussing on the 65 million year old Mexican crater.
We read of tsunami deposits in Texas and Haiti, geophysical identification of the buried crater in the Yucatan, discovery of microtektite spherules in the boundary layer, and the discovery and dating of melt rocks. Strangely, Alvarez's personal turning point came later, in 1992: he tells of a moment of epiphany in the central plaza of a small Mexican town.
Sticking close to his own role and expertise, Alvarez omits other elements of the K-T story. His father's idea that the dinosaurs, at the top of the food chain, died from starvation due to the collapse of photosynthesis during year-long darkness is introduced but never analyzed. He does not discuss (except in a prologue) the many other environmental consequences of impact that have been researched in the last 15 years. Much antagonism of paleontologists to the Alvarez idea that the dinosaurs died out suddenly involves their inability to reconcile ostensible killing mechanisms with the fossil record. Yet Alvarez doesn't choose in this book to try to address most of their concerns.
Toward the end, Alvarez mentions without amplification a few unresolved issues, such as whether other mass extinctions in the geological record might be due to impacts. He closes with a brief reflection on the symbolism of the crash of comet Shoemaker-Levy 9 into Jupiter. One can read "T. rex" in a single sitting and I recommend it highly -- if only as a jumping off point to other perspectives on this dramatic scientific revolution.
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Available Abstracts, Preprints, Articles.
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R. Chapman's Publications.
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