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Named for James Hutton, the Scottish geologist who first described this geological phenomenon in the late 18th century, the unconformity at Siccar Point was pivotal in kick-starting modern geology.

The unconformity itself is the result of the juxtaposition of two distinct rock formations, with the older formation, the Old Red Sandstone, lying unconformably on top of the younger, older in geological time, Silurian greywacke rocks. This relationship is significant because it demonstrates that there have been long periods of time during which no sedimentation occurred, and that the Earth's geological processes have been operating consistently over vast timescales.

The Old Red Sandstone formation, which is the older of the two, is characterized by its distinctive red color due to iron oxide and is predominantly composed of sandstone, siltstone and shale. This unit was deposited during the Devonian period, around 385 to 360 million years ago. The Silurian greywacke, on the other hand, predominantly consists of mudstone, siltstone and shale, believed to have been deposited around 435 million years ago.

The history of the place can be traced back to the late 18th century, when Hutton first described the unconformity at Siccar Point. Hutton's observations challenged the prevailing views of his time, which held that the Earth was a young planet, and that its geological features had been formed in a cataclysmic event. Hutton's work laid the foundation for the modern scientific understanding of geology, and his ideas were later developed into the principle of uniformitarianism, which holds that the geological processes that have shaped the Earth in the past continue to operate in the present.

I'd been meaning to go visit such a noted site for a couple of years - mission accomplished!