Ann Blair, CB20 Lecture 18: geology I. 17th ct views of history of the earth • Age of earth estimates from combining Bible with ancient history, e.g. archbishop Ussher: Creation on Sun Oct 23, 4004BC • Fossils as jokes of nature (16th) or effects of Noah’s Flood • Speculative histories of earth based on principles of mechanical philosophy (e.g. William Whiston, New Theory of the Earth, 1696) II. 18th century • Many new empirical observations: stratigraphy, mineralogy, fossils; eruptions and earthquakes • 2 theoretical camps: Neptunism : rocks formed by precipitation from water, e.g. in Flood. vs. Vulcanism: rocks formed by heat and pressure but also volcanic eruptions—need longer time but still a focus on catastrophe • First deep time: Georges Buffon (Epoques de la nature, 1778): 6 days=6 ages of indefinite length (earth age at 75’000 - 3 million years). Age of earth cut loose from age of humankind (which matches biblical creation) III. James Hutton (1726-97): Theory of the Earth (1788) • Sedimentation, elevation by heat & pressure, erosion • “no vestige of a beginning, no prospect of an end” • defended by John Playfair, a natural theologian and minister “It is but reasonable that we should extend to the geologist the same liberty of speculation which the astronomer and the mathematician are already in possession of; and this may be done by supposing that the chronology of Moses related only to the human race." Playfair as quoted in Greene, p. 81. IV. Charles Lyell: Principles of Geology (1830-33) • =the other book that Darwin took with him on the Beagle voyage • uniformitarianism (rather than catastrophism) • need deep past of earth; fossil record not complete • professional geology: proceed “as if Scriptures did not exist” Terms to retain: Uniformitarianism, catastrophism, fossil record, vulcanism, neptunism, Hutton, “no vestige of a beginning, no prospect of an end”, scriptural geology, Lyell, Buffon .