Hutton's Section: The Rock That Proved the Earth Is Old
Why is it significant?
Near the southern end of the crags, just above the road, look for a patch of cliff marked by an information board. It does not look like much: a band of dark rock sitting on top of paler, layered stone. But geologists come here from all over the world as if on pilgrimage. This is Hutton's Section.
Key Facts
| Place | Hutton's Section: The Rock That Proved the Earth Is Old |
|---|---|
| Address | Hutton's Section, Queen's Drive, Holyrood Park, Edinburgh EH8, UK |
| Geo Coordinates | 55.94310, -3.16730 |
| Part of Walk | Climbing a Volcano: Arthur's Seat & Holyrood Park, Edinburgh |
| Generated | Generated |
Near the southern end of the crags, just above the road, look for a patch of cliff marked by an information board. It does not look like much: a band of dark rock sitting on top of paler, layered stone. But geologists come here from all over the world as if on pilgrimage. This is Hutton's Section. Depending on the fencing along the Radical Road, you may have to admire it from a short distance.
In Hutton's day, most experts followed the Neptunists, who believed that all rocks had settled out of a vast primeval ocean, layer after layer, like sediment in a glass of muddy water. If they were right, the dark dolerite on top should simply be one more layer laid down on the one beneath. Hutton had a different idea. He thought this rock had come from below, as a hot liquid, pushed into the layers from underneath.
And here was his evidence. Look closely at the boundary. In places the dark rock cuts across the layers below it, and it has broken off chunks of the sediment and swallowed them whole. The sedimentary rock right at the contact looks baked and altered, as if it had been in an oven. Mud settling gently on a seabed does not do that. Molten rock forcing its way in does. The history of the earth was written, quite literally, at the bottom of this cliff.
It sounds obvious now, but the battle between the Neptunists and Hutton's followers, the Plutonists, named after the god of the underworld, raged for decades and split the lecture halls of Edinburgh. Hutton's side won. The idea that the earth is shaped by heat, uplift and slow erosion over immense stretches of time became a foundation of modern geology, and it was carried forward by Charles Lyell, whose books the young Charles Darwin took with him on the Beagle.
One small request: please do not hammer or chip the rocks. This is a protected site, and every geology class that comes after you wants to see it too. Now cross into the valley to the east and follow the path that runs north along the floor of Hunter's Bog, with the crags on your left and the bulk of Arthur's Seat on your right.