Competing theories attempt to explain the extinction of the dinosaurs. The last species of dinosaur lived in the Cretaceous period, which extended from about 144 million to 65 million years ago. By the beginning of the next period, called the Paleogene period, the dinosaurs had died out. The time between these two periods is commonly called the "K/T Boundary." In 1980, two scientists postulated that a giant meteor strike caused global climate changes that obliterated the massive creatures and many other life forms. Scientists had many clues, but they needed evidence that the meteorite impact and mass extinction happened at the same time. With photographs, diagrams, and crisp text, paleobiologist Richard Norris brings the scientific process to life as he recounts how his Woods Hole expedition collected evidence to support the K/T impact theory. Researchers pulled mud from the ocean floor and examined it to see if impact debris formed at the same time that ocean creatures became extinct. They also analyzed the climate changes that would have followed the meteor blast to see if this was consistent with the species that lived and died. This book, part of the "Turnstone Ocean Explorer Series," is sophisticated science--yet fun to read and easy to remember.