When I walked the Berwickshire Coastal Path in the winter I meant to go down to Siccar Point, the site of a famous feature known as Hutton’s Unconformity, and just didn’t have time, which I was disappointed about – so recently I finally got round to going back there, because it’s not often that you get to see Enlightenment science just sitting there in front of you!
An unconformity is a gap in the sequence of rocks – in this case the older rocks are 65 million years older than the newer rocks – and if I’m understanding it correctly, the point is that this gives time for the older rocks to have been worked on in various ways – squashed and folded and worn away. And the real point is the sheer amount of time this must have taken – Hutton‘s work in the 1780s is the start of the move from biblical time to geological time.
At Siccar Point the older rocks are greywacke (and definitely grey), tipped up until the strata are almost standing on end, and the newer rocks are red sandstone, still in vertical layers – Hutton’s trip there to study the rocks was by boat, but it’s all quite visible looking down from the top of the point.
It’s probably only visible if you can land by boat, and even then possibly only to an expert, but one thing that really excited Hutton was that the older rocks still show ripple marks from having been laid down in water, as well as the results of later pressure – another sign of gradual processes, not one great cataclysmic event.
Hutton owned farms in the area, and it seems to have been work on improving the land which first raised his interest in geology – he had already been involved in chemistry experiments and a chemical business.
It wasn’t on the signs at the point, but I know I’ve read somewhere that it was the mix of red and grey stones in the field walls that set him looking in this area for what he wanted, and it’s still a striking local feature today!