This survey of four-and-a-half billion years of Earth's past is a splendid introduction to geology and paleontology for the lay reader. MacDougall, a professor of earth science at the Scripps Oceanographic Institute (UC-San Diego), takes us step-by-step through the geologic time scale. Clues to the past lie in rocks, in oxygen isotopes and on the ocean floor. MacDougall traces the rise of continents and the origins of life in each era. He discusses tectonic plates, the major extinctions and their probable causes, climate and the Ice Ages, and he speculates on the future of our planet. To compress Earth's history into a single, lucidly written volume is a major achievement.
