Annals of the Former World, by John McPhee

The earth is about 4.5 billion years old. The first terrestrial plants appeared about 400 million years ago and aerobic life (humans are aerobic creatures, as are amoebae – well, they can be anaerobic too, and many bacteria) appeared somewhere between 500 million and 1 billion years ago. Think about this – a full 90% of the earth’s history had no land vegetation. Photosynthesis? a few billion years ago. The “Cambrian” explosion was around 500 million years ago when large life forms emerged en masse; these were not the “dinosaurs” that we all know and love. These were earlier creatures that were essentially wiped out during the Permian extinction around 250 million years ago (we don’t know what happened). Dinosaurs emerged after this catastrophic event during the Triassic period and hung around until 65 million years ago at which time another catastrophic event wiped out most life on the planet (?asteroid collision). Are these numbers meaningful? We cannot fairly relate to the enormity of this expanse of time. McPhee writes, “…geologists will sometimes use the calendar year as a unit to represent the time scale, and in such terms the Precambrian runs from New Year’s Day until well after Halloween. Dinosaurs appear in the middle of December and are gone the day after Christmas. The last ice sheet melts on December 31^st at one minute before midnight, and the Roman Empire lasts five seconds.” Some perspective. This voluminous work covers many years of McPhee’s life as he traveled around the country with geologists learning about the American terrain and how it came into being. Interwoven are amusing and sometimes fascinating accounts of the people that have come up with the theories and the history of the study of Geology. This tome is a joy to read, although sometimes difficult to understand (unless you are a geologist which I am not). Nevertheless, it is well worth the effort. Informative, entertaining, and humbling. We would do well to learn about the rock under our feet.