"The mind seemed to grow giddy by looking so far back into the abyss of time."
John Playfair upon observing Siccar Point, 1788
Siccar Point is a rocky promontory situated forty miles east of Edinburgh, Scotland in Berwickshire. To the untrained eye, it is a picturesque outcrop of rocks jutting into the waters of the North Sea. A horizontal layer of reddish sandstone sits atop near-vertical layers of what is called greywacke. The sandstone comes from sediments deposited by a desert. The greywacke formed from marine muds deep at the bottom of an ancient ocean. This unassuming rock exposure played a crucial role in advancing our understanding of the earth, and more importantly, helped change our views on man's place within the universe.
The latter half of the 18th century saw an outpouring of intellectual and scientific endeavors in Scotland dubbed the "Scottish Enlightenment". Notable thinkers and inventors such as philosopher David Hume ("A Treatise on Human Nature"), economist Adam Smith ("Wealth of Nations"), and James Watt. Scotland had a long tradition of supporting education, and by the 18th century, their universities rivaled those on the continent. They attracted a wide array of intellectuals who pursued a multitude of passions from natural science to commerce to theology. Edinburgh was the center of this activity, and it was here in 1727 that James Hutton born.
Hutton was the son of a merchant who died when Hutton was very young. Like most children who lived in Edinburgh, he attended the Royal High School of Edinburgh. Here he became interested in chemistry and mathematics. At the age of 14, he started classes at the University of Edinburgh where he studied the classics in preparation for becoming a lawyer. He had more of an interest in science than law, so he became a physician's assistant and started taking medical classes. After three years at Edinburgh, he transferred to the University of Paris where he eventually earned a degree as a Doctor of Medicine. Back in Scotland, he partnered with a friend in a profitable business of manufacturing crystal salts used in dyes and metalworking. Many of these replaced natural salts that were expensive and had to be imported. In the 1750's he settled on the family farm he inherited from his father located in the lowlands of Berwickshire. He developed an interest in agriculture and husbandry, and he experimented with ways to improve the agricultural practices of Britain. This led to a study of the weather and to geology.
Hutton grew up under the influence of the culture of intellectualism that had blossomed in his native Scotland. Not just a mere gentleman farmer, he had a philosophical outlook, a passion for natural science and scientific inquiry, and a keen sense of observation. Overseeing his farm, he had the opportunity to observe the interplay between the land and the forces of wind and water. He studied the processes of erosion and deposition as well as contemplating the causes of uplift. Over the course of fourteen years, he pieced together his observations into an outline of a theory. He began seeing these processes as cyclical. The Earth, he imagined, had gone through periods of deposition then uplift then erosion repeated again and again. Natural scientists, they called themselves "natural philosophers", had already come to agree that the bedrock of the Earth was long, parallel layers reposing at different angles. These rocks were made of sediments that had been deposited in water and compressed to form stone. Hutton believed, from his observations, that these processes occurred slowly over long periods of time. He imagined that these rocks were made from “materials furnished from the ruins of former continents.” For awhile, Hutton shared his speculations with only a small circle of friends. He needed evidence to support his theory. Then he visited Siccar Point and knew this was the evidence he needed to confirm his theory.
Hutton traveled to Siccar Point in 1788 along with two companions, Dr. James Hall and John Playfair. This exposed outcrop, Hutton realized, provided clear evidence of the processes he had studied and theorized about. He described the sharp juncture between the vertical greywacke and the horizontal sandstone. He deduced that a considerable amount of time had been required for the greywacke to be tilted upward and then eroded before the sandstone could be deposited over it. Without realizing it, Hutton had come up with the notion of deep time. The idea that the Earth was immensely old. In Hutton's time, the age of the Earth was unknown. The most accepted number was calculated by the Archbishop of Ireland, James Ussher. He determined, through a study of the Bible, that the Earth was 6,000 years old. This put the date of creation at 4004 B.C. - October 22. This became the accepted age by the Church. Today, through radioactive dating, we can estimate that the Earth is at least 4.5 billion years old.
What Hutton described at Siccar Point is today called an unconformity. (This one has been named Hutton's Unconformity. The famous "Great Unconformity" can be seen in the bottom layers of the Grand Canyon.) An unconformity is a break in the sequence of rock layers. The boundary between strata represents a time period in which erosion occurs but deposition of sediments has ceased only to resume at a later timeframe.
In his work, Hutton also advanced the idea that the processes that we can witness today are the same ones that occurred in the deep past. And they will continue to happen in the future. Later, British geologist Charles Lyell will use this idea to develop his principle of uniformitarianism.
After visiting Siccar Point, Hutton published his book "The Theory of the Earth" in 1788. He would republish it in 1795 as a multi-volume work. With this work, James Hutton is considered the "father of modern geology". Having been trained in other sciences, he brought to the young science of geology the same empiricism, experimental methods, and rational thought seen in other disciplines. Yet his influence goes beyond the science of geology. By implying the immense age of the Earth, he directly challenged established Christian doctrine and Biblical authority. The timespans needed to create a Siccar Point meant that the Bible could no longer be read as a literal text. Mankind arrived late to creation. On the other hand, Hutton's work made possible Charles Darwin's theory of natural selection. Those same timespans that allowed the landscape to change through the processes of erosion, deposition, and uplift could also allow for the gradual changes to plants and animals in the form of evolution. The idea that processes we observe today happened in the deep past meant that the process of natural selection has always occurred as well. Our whole paradigm about time changed. If the Earth is very old, what about the moon, the sun, the planets, or the stars? What about the universe itself? These are questions that scientists began exploring after Hutton.
James Hutton had the imagination to look at Siccar Point and connect what he read in those rocks to what he observed daily on his farm. Siccar Point remains a mecca for geologists and geology students. Even as it tells us about Earth's past, it is subject to those same erosional forces of wind and water, and its sediments are being deposited at the bottom of the North Sea. Sometime in the future, the material that makes up Siccar Point will be part of some future continent.
Further Reading
The Blasphemous Geologist Who Rocked Our Understanding of Earth's Age: Jim Morrison (Smithsonian Magazine)