I read and greatly enjoyed Steve Brusatte’s The Rise and Fall of the Dinosaurs back in the fall, and made a note to pick up a book to which he referred many times, Walter Alvarez’s delightfully titled T. rex and the Crater of Dooooooooom (I may have added a few o’s there). Alvarez, an earth sciences professor at Cal Berkeley, developed the hypothesis that a massive impact of a non-terrestrial object wiped out the dinosaurs and ended the Cretaceous period in what is now known as the K-Pg or K-T extinction event. Along with his father, Luis, and numerous other scientists from multiple disciplines, Alvarez worked on the hypothesis and led the search for evidence, eventually finding enough evidence that the hypothesis is considered the correct explanation for the mass extinction. In this quick 150-page book, Alvarez retells the story of the development of the hypothesis and the global hunt for proof as well as the scientific fights over this specific hypothesis and the challenge it posed to the previous orthodoxy of uniformitarianism – the idea that changes to the earth were gradual and not caused by catastrophes like an asteroid or comet impact.

The scientific consensus on the K-T extinction event is well-established now, and Alvarez begins the book with a description of what likely happened the day that a giant rock, around 10 km in diameter, slammed into the northwest portion of what is now the Yucatan peninsula of Mexico, creating the Chicxulub crater on land and beneath the Gulf of Mexico. The impact took place 66 million years ago, so in the interim it had been largely covered by additional layers of sediment and rock on land, and thus its discovery was delayed until someone was actually looking for it in the first place. The Chicxulub impact was catastrophic on a scale unimaginable to us today; a rock that was wider than the height of Mount Everest slammed into the earth, releasing a billion times more energy than that created by the atomic bombs the U.S. dropped on Hiroshima and Nagasaki. This impact was so powerful it vaporized gypsum in the earth, created tektite glass nodules, led to seismic waves in the rock itself, and would have killed anything living within several hundred miles of the impact site through heat or fire. The impact also kicked up enough dust, including the iridium that would settle in a consistent layer around the planet, to lead to a year or more of a de facto winter where sunlight was blocked enough to halt photosynthesis and devastate the global biosphere.

The hypothesis itself was controversial because of that previous orthodoxy that all changes to the earth occurred gradually, which dated back to Charles Lyell in the early 1800s and influenced the work of Charles Darwin. Alvarez’s heresy, that a single, massive, external catastrophe permanently altered the shape of the earth’s surface and the course of life on the planet – wiping out the dinosaurs and creating a massive ecological void that would be filled by large mammals, including us – encountered immediate pushback, some of which persists today even though the evidence in favor of the impact hypothesis is substantial. Alvarez walks through the history of the development of his hypothesis, including why it was never taken seriously before, and the scientific battle that followed it up through the 1990 discoveries that led to the conclusion that the impact that caused the Chicxulub crater was the same one that killed the dinosaurs.

Alvarez’s writing is on the dryer side, unsurprising given his background as scientist, but the story itself carries the book through – this was an earth-shattering (pun very intended) discovery, and it shook the foundations of an entire field of science. It’s a worthy read on its own but also a great reminder of the power of entrenched thinking, and how many earth scientists and geologists continue even to this day to fight against the preponderance of evidence that Alvarez’s hypothesis is correct. (We know the crater exists, so we know something very large hit the earth there, but there are arguments that, for example, the impact didn’t cause the global iridium layer, even though nearly all iridium in the earth’s crust came from extra-terrestrial sources.) He also makes sure to credit many, many other scientists who helped along the way, emphasizing that the search for evidence to support or contradict the hypothesis was a multi-disciplinary effort that spanned the globe and took over a decade, which is a kind gesture but did tend to slow the story down for me. It’s a short enough book that this was never really a problem, although I think Brusatte does a better job of explaining the Alvarez hypothesis for the lay audience than Alvarez himself does here in more academic fashion.

Next up: Still reading Iraj Pezeshkzad’s very funny novel My Uncle Napoleon.