LYELL’S ELEMENTS OF GEOLOGY (1838) AND THE ORIGINS OF THE CLASSIC ROCK CYCLE DIAGRAM

Often credited as the “father of modern geology,” James Hutton (1726-1797) proposed two innovative constructs for the origin and theory of the Earth: 1) modern processes operated in essentially the same way, within the same time frame, in Earth’s past; and 2) granite had molten origins. While geologic time provided the temporal reference within which a multitude of events could plausibly occur, it was the molten origin of granite that would eventually connect rock types and their recycling/transformation within a “rock cycle,” considered to a main theme of basic geology.

Hutton’s 1795 book, Theory of the Earth with Proofs and Illustrations (2 volumes), provided the ideas and concepts for the development of the modern rock cycle diagram. However, Hutton did not diagrammatically map his new constructs for the reader: there are 4 fold-out plates in Volume I, and another 1 plates in Volume II, but figures consist of proxy images of septarian nodules and landscape scenes. In the late 1700s, diagrams and figures were expensive to reproduce, and had to be printed and inserted separately from the narrative.

When Charles Lyell (1797-1875) promoted and popularized Huttonian theories, printing techniques via wood engraving had advanced to facilitate inexpensive, multiple images directly inserted in a text. Lyell illustrated his Principles of Geology volume I (1830) with 33 figures and 2 map plates; volume II (1832) with 9 figures; volume III (1833) with 93 figures and 5 plates. However, it was not until Lyell repackaged his theories into a general geology text that a rudimentary rock cycle diagram appears. Lyell’s Elements of Geology (1838) features an “Ideal Section of the Earth’s Crust” in cross section, complete with aqueous (sedimentary) rocks, volcanic/plutonic rocks, and metamorphic rocks. The hand-colored frontispiece is the earliest illustration of the rudimentary rock cycle uncovered in an investigation of geology texts from 1788 through 1840.