T. rex and the Crater of Doom; Walter Alvarez; 1997; Princeton University Press; 146 pgs, index, notes

This book is better than its sequel, A Most Improbable Journey. It deals with larger issues and documents one of the great over-arching discoveries of the 20th century, namely that the Earth was hit by a 10 km wide rock in the Yucatan that wiped out the dinosaurs as well as many other kinds of creatures, such as the ammonites (nautilus like critters that ruled the oceans for millions of years). This all took place October 29, 65,000,0000 years ago, at 9 AM in the mourning. 


The impact was stupendous. The rock was so big, it's leading edge was grinding a huge hole (the Chicxulub Crater) in the Earth while the trailing edge was still in the upper atmosphere. A second later, it was all over but for the fallout, burning atmosphere, huge tsunamis, and a stifling hot (due to released  CO2) "winter", and dust that blacked out the sky.


The simultaneous exploding of every nuclear weapon on Earth would be like a fart in the wind by comparison.


The story of the discovery surrounds the KT boundary, a thin layer of clay that marks the end of the Cretaceous (and the dinosaurs) and the start of the Tertiary (the first  layer of which  is the Danian, after the Danish site where it was first described).


The idea was floated that a impact may have killed the dinosaurs. Walter's famous physicist Dad, Luis, suggested looking for a radioactive isotope of an element that is found in meteors, but generally not on the Earth's surface, in the KT boundary. Iridium was the final choice. The other "tell" is something called "shocked quartz, which I will leave to reader to find out about.


Skip to the end: Iridium was found all over the word in the KT (K is used because C was taken, and it also came from the German for chalk).


This is where the story is different from other scientific detective stories. I cannot recall a discovery that had so many scientists excited from so many disciplines. Geology, of course, but paleontology, archeology, planetary astronomy, astro-physics, nuclear physics, chemistry, biology, the physics of impacts, and so on. Soon, evidence was popping up in multiple fields at once, and an idea that was poo-poo-ed became accepted fact in a just a few short years. Sadly Luis died before his idea bore fruit.


This is a very approachable book, and a quick must-read for any student of the processes of science (aka human knowledge). Since then ( around 1990), 130 more ancient craters have been found.    

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