Siccar Point: A Day In The Field At Hutton’s Unconformity

Siccar Point – In June, 1778, James Hutton, John Playfair, and James Hall gazed on the rocks at Siccar Point and understood that an immense amount of geologic time was needed to produce the juxtaposition of underlying vertically-oriented (Silurian graywacke) bedded rocks with overlying near-horizontal (Devonian, Old Red Sandstone) rocks.

Siccar Point is unquestionably one of the most important geological sites in the understanding of geological time. It was here in 1778 that James Hutton, John Playfair, and James Hall contemplated the immensity of time needed to produce vertically oriented rocks overlain by gently-dipping rocks. The concept of geological time is so fundamental to the science of geology that I really wanted to explore the locality that gave rise to the idea of geological time. So I finally made the trip to Scotland and Siccar Point a couple weeks ago. Wow – what an amazing country! It was a fantastic trip, but for this blog, I’ll just post a few photos of Siccar Point – just enough, perhaps, to encourage geologic time enthusiasts to also make the trip.

Siccar Point is located  on Scotland’s Berwickshire coast, about 40 km southeast of Edinburgh. It is not difficult to get there from Edinburgh if you’re willing to drive a few back roads, and also drive on the left side of the road – which for me was somewhat of an initial challenge (going left on the roundabouts was mind boggling to begin with!). The best directions that I found for getting to Siccar Point are given by Angus Miller, who also runs field trips there. Angus’s directions to Siccar Point and his contact information are found at his Geowalks website.

The gate into the fields for the hike to Siccar Point.

The pull-off for the hike to Siccar Point is well marked by signage. All that one needs to do is walk through the gate and then follow the fence lines south to the Siccar Point locality. There is a small sign on the entrance gate that advises you to beware of the bull. We happened to meet up with a local person while we were hiking through the fields to Siccar Point and she told us that the land owner posted the sign mainly because he’s at war with the hordes of people that tromp through his fields to get to Siccar Point (in Scotland there is the “right to roam”, so one can hike across private property). She also assured us that at the time we were there, the cows were off in another field, so not to worry about the bull. We then just followed the hiking instructions on the sign at the gate entrance, and found that it’s an easy walk to Siccar Point.

The entrance sign to Siccar Point with hiking instructions.
The ruins of the St. Helen’s Chapel are found near the start of the hike to Siccar Point.
Much of the hike to Siccar Point is at field edges, near the sea cliffs.
The fence lines finally give way to the rock promontory that is Siccar Point.

Once one arrives at the rock promontory that is Siccar Point, it is an amazing view looking down the cliff face. The vertical beds of Silurian graywacke outcrop beautifully below Devonian Old Red Sandstone. The “Hutton Unconformity” here marks an approximately 80 million year hiatus. Again, there is also good signage present at the promontory for an explanation of the unconformity.

Siccar Point – the rock promontory that contains Hutton’s Unconformity.
Signage at Siccar Point well explains Hutton’s Unconformity.
A view to the south of Siccar Point where the underlying vertical beds of Silurian graywacke snake along the coast line, under the more gently dipping beds of the Devonian Old Red Sandstone.

 

 

 

 

 

A rope is attached to the fence at the promontory to help the climber down the cliff face. As it was a muddy and slick climb down to the North Sea, I was very glad to use the rope! Much thanks to whoever put the rope there!

Roping down the cliff face was a welcome way to get to the rocks below.
The rope climb back up Siccar Point – once again, I was very appreciative of the rope being there!

It was fun to investigate the unconformity at the sea’s edge. The base of the Old Red Sandstone contained lags from the graywacke, some of which are cobble size.

A closer view of Hutton’s Unconformity with the Old Red Sandstone atop the Silurian graywacke.
A layer of lag clasts at the base of the Old Red Sandstone. The vertically-oriented beds of the Silurian graywacke can be seen beneath the Old Red Sandstone.
A view back up the cliff face gives a good visual of the gently dipping Devonian Old Red Sandstone overlying the vertical beds of Silurian graywacke.

I know that we were very lucky to have good weather for our Siccar Point excursion, but I would have gone there whatever the weather. It is really one of the great geologic sites and well worth traveling part way around the world to see. For a drone view of Siccar Point, take a look at the video done by the British Geological Survey which is posted in an earlier Geopostings blog: Siccar Point from a drone’s view.

 

 

 

Siccar Point – The Roots of Modern Geology

Siccar Point, located on the southeast coast of Scotland, is well revered in the geological community. Outcrops at this locale display ‘Hutton’s Unconformity’. This is an angular unconformity where tilted rock units of about 370 million years in age called the Old Red Sandstone (with a basal layer of conglomerate) lie atop nearly vertical strata of greywacke that are approximately 435 million years in age. James Hutton observed these rock juxtapositions while on a boat trip past Siccar Point in 1788 with James Hall and John Playfair. His observations and contemplation of this unconformity formed a basis for his theory of repeated cycles of deposition, uplift, and erosion, which was later known as uniformitarianism.

The British Geological Survey posted a new video on Siccar Point a few days ago. Their video features amazing drone video of the locale and good accompanying audio. It is well worth a view!