Siccar Point is a geologic landmark located just under 40 miles from Edinburgh, Scotland. It was made famous by Scottish geologist James Hutton (1726–1797), who is considered to be the father of modern geology. Hutton was the first to understand that geologic processes take place over millions of years, rather than the biblical estimation of 6,000 years that was prevalent in his time.

Hutton was also first to realize that these processes are still ongoing, and that the Earth is continually being reshaped by forces that uplift rock, wear it away, deposit it as sediment, and compress it into rock again.

Siccar Point
Siccar Point. Credit: Dave Souza, Wikipedia

While his contemporaries believed that sudden cataclysmic events like the biblical flood were responsible for the landscape they saw, Hutton believed that geologic processes occur at a relatively steady rate over time, and that people could learn the age of the Earth by observing the rate at which those processes occur.

Hutton traveled throughout Scotland to do just this. At Siccar Point, he found an unlikely juxtaposition of slightly tilted red sandstones overlaying harder, almost vertically-pitched gray shale. The sharp contrast between the mismatched layers was puzzling.

Hutton was able to infer that the gray shale had been uplifted, tilted, significantly eroded, and then covered by an ocean. This ocean deposited the sand that later became the red sandstone.

The erosion of part of the gray shale left a gap in the geologic record with no rock to represent the period of time in which it formed. Such gaps are called unconformities.

The point of contact between the two rock types at Siccar Point is now called the Hutton Unconformity. It is one of several unconformities that Hutton discovered.

Siccar Point is an angular unconformity, in which horizontal layers of sedimentary rock sit directly atop tilted and eroded layers.

Hutton understood that the sequence of events that occurred at Siccar Point must have taken place over an enormous amount of time, and that the Earth must therefore be vastly older than commonly believed in his era.

His ideas about the slow and steady rate of geologic change formed the basis of uniformitarianism, a fundamental principle of the geosciences that holds that the landscape changes slowly over time.

Learn more about different ideas about how the Earth was formed and how we have calculated the age of the Earth.