We started our geology walk in Edinburgh's James Hutton Memorial Garden, which was constructed in 2001 for the University of Edinburgh on the site of the house and garden of James Hutton (1724-1797). The garden contains a memorial plaque and 5 boulders which illustrate 2 of the main themes of Hutton's geological work.

James Hutton (1726–1797), a Scottish farmer and naturalist, is known as the founder of modern geology. He was a great observer of the world around him. More importantly, he made carefully reasoned geological arguments. Hutton came to believe that the Earth was perpetually being formed; for example, molten material is forced up into mountains, eroded, and then eroded sediments are washed away. He recognized that the history of the Earth could be determined by understanding how processes such as erosion and sedimentation work in the present day. His ideas and approach to studying the Earth established geology as a proper science. In the late eighteenth century, when Hutton was carefully examining the rocks, it was generally believed that Earth had come into creation only around six thousand years earlier (on October 22, 4004 B.C., to be precise, according to the seventeenth century scholarly analysis of the Bible by Archbishop James Ussher of Ireland), and that fossils were the remains of animals that had perished during the Biblical flood. As for the structure of the Earth, “natural philosophers” agreed that much bedrock consisted of long, parallel layers which occurred at various angles, and that sediments deposited by water were compressed to form stone. Hutton perceived that this sedimentation takes place so slowly that even the oldest rocks are made up of, in his words, “materials furnished from the ruins of former continents.” The reverse process occurs when rock exposed to the atmosphere erodes and decays. He called this coupling of destruction and renewal the “great geological cycle,” and realized that it had been completed innumerable times. Another of Hutton’s key concepts was the Theory of Uniformitarianism. This was the belief that geological forces at work in the present day—barely noticeable to the human eye, yet immense in their impact—are the same as those that operated in the past. This means that the rates at which processes such as erosion or sedimentation occur today are similar to past rates, making it possible to estimate the times it took to deposit a sandstone, for example, of a given thickness. It became evident from such analysis that enormous lengths of time were required to account for the thicknesses of exposed rock layers. Uniformitarianism is one of the fundamental principles of earth science. Hutton’s theories amounted to a frontal attack on a popular contemporary school of thought called catastrophism: the belief that only natural catastrophes, such as the Great Flood, could account for the form and nature of a 6,000-year-old Earth. The great age of Earth was the first revolutionary concept to emerge from the new science of geology.