Chapter 4 by Andrea Guinanzaca

Chapter 4 was about how many millions of years ago ammonites, dinosaurs, and other species competed during the Cretaceous period with the purpose to survive. The chapter opens with the famous extinction story known as dinosaurs becoming extinct million years ago because an asteroid killed them. Walter Alvarez, was a scientist that was studying plate tectonics until he found layers of marine fossils. Then in those layers, he realized that they were thick layers of clay. He collaborated with his father Luis Alvarez, and together they investigated the unusual thing and discovered that the that the layers of marine fossils were traces of huge asteroids because they contain huge amounts of iridium and iridium. They also found out that the layers of clay dated back to the end of the Cretaceous period. Together, the Alvarez’s created the theory that explained the new evidence they discovered. However, their theory was categorized as falsifiable. The chapter also talks about Kolbert's travels to another place and this time she goes to Princeton. In Princeton, she meets Neil Landman. In this part of the chapter Kolbert watches Landman and his peers investigate ammonite fossil sites. Landman explains how ammonites died out very quickly along with the dinosaurs in the Cretaceous period. In this part of the chapter, ammonites are compared to nautiluses. They realize how their characteristics are very much alike which makes sense that the nautiluses are descendants of the Ammonites. In conclusion, the chapter sums up how the terms catastrophism and uniformitarianism go in hand in hand meaning that these two theories coexist and that natural selection is a process that is completed slowly throughout time which supports the theory of evolution.