This book explores the development of ideas about enormous floods, both gradual and catastrophic, and the role of floods in fashioning the Earth's surface. Floods of immense size are recorded in ancient myths and classical writings. Renaissance scholars believed that sea shells found on mountains were relics of Noah's Flood, and natural philosophers during the Restoration and Enlightenment proposed elaborate theories of the Earth which accounted for a universal Deluge. During the late eighteenth and nineteenth centuries, field evidence suggested that there had been several grand cataclysms during the course of Earth's history, the most recent of which was identified with the Noachian Cataclysm. In the nineteenth century too, a gradual inundation of continents was proposed, an idea which was taken up by proponents of marine regression and transgression cycles. During the present century the notion of marine transgression has been refined. Recently, the possibility of catastrophic flooding has again been raised. The author traces the developments of each of these theories and provides a comprehensive bibliography of the exploration of these ideas through the centuries.