#siccar point

[grrlmusic]

Intertoto - Siccar Point

[geologicaltravels]

2013: From looking at Google Maps, the signage has not been updated in the last 10 years changing the stated duration of the unconformity of 55 million years to a more likely value (according to IUGS) of approx 75 million years? Siccar Point is one of the top 100 Geoheritage sites in the world.

[azvolrien]

Additional Rock Facts: this, here shown covered in geology students (it’s an old photo), is Hutton’s Unconformity at Siccar Point, a small headland in the Scottish Borders just east of Pease Bay Caravan Park. Also named after James Hutton; dude got around. The significance of this one is that, as an angular unconformity (i.e., the rocks are of different ages and don’t line up), the differing directions of the strata show that a) geological deformation has changed the orientation of the older rocks (behind the person in the middle) from how they were originally laid down and b) there have been lengthy interruptions in the process of sedimentary deposition. This may seem obvious to us today but in Hutton’s time it was contrary to the accepted wisdom that the rocks we see today were deposited after the single cataclysmic flood of Noah’s Ark fame. The person with the blue rucksack is sitting at the margin; the older grey rocks were lifted up so that the strata were vertical, erosion smoothed out the surface, and then the reddish rock was laid down on top.

[earthstory]

Siccar point by drone. Original caption:

Not far from Edinburgh, Siccar Point is a rocky promontory that has become a place of pilgrimage for geologists from across the globe.

James Hutton, father of modern geology, visited Siccar Point by boat in 1788, an event which led to a profound change in the way the history of the Earth was understood.

A man ahead of his time, James Hutton used the evidence from Siccar Point to decode Earth processes and to argue for a much greater length of geological time than was popularly accepted. As John Playfair later recorded of their visit “The mind seemed to grow giddy by looking so far into the abyss of time”. A concept of ‘deep time’ emerged with the recognition that the geological processes occurring around us today have operated over a long period and will continue to do so into the future.

James Hutton found the decisive evidence he sought for his Theory of the Earth, Hutton’s Unconformity, the never-ending cycles of creation and destruction that shape our landscape today.

Hutton’s theory overturned the last vestiges of the Biblical account of a world shaped by the receding waters of a universal flood. Controversial in its day, Hutton’s work is now a foundation stone in the science of geology.

You can visit Siccar Point today, and see the spectacular junction between two distinctive types of rock, just as Hutton himself found it.

Client: Dynamic Earth / Juniper Leaf Education Production & Post: Play North Music: Kai Engel | Marée | Brum

[geologicaltravels]

2013: Name a more famous outcrop in geological science.

[earthstory]

Siccar Point

The US Geological Survey’s Landsat 8 satellite captured this image of Siccar Point in Scotland, perhaps the most famous angular unconformity on Earth. At this site, naturalist James Hutton recognized that the presence of an angular unconformity required millions of years of Earth history – the first layer of rocks had to be formed, tilted, and eroded, before another layer could be deposited on top. What I particularly like about this image is that if you look along the shoreline to the west of Siccar point, you can actually see the pattern created by the dipping beds of the Old Red Sandstone. There are linear outcrops all along the shoreline that outline the intersection of those beds with the surface – that direction is what geologists call the strike. It even looks like one of the creeks follows that direction for a short distance. To the right of Siccar point, you can no longer see this pattern, as the older and steeper beds strike in a different direction.

JBB

For more on Siccar point, see our previous posts: https://tmblr.co/Zyv2Js11Z9mNF https://tmblr.co/Zyv2Js1R6HJsL https://tmblr.co/Zyv2Js221GUwo

Image credit: https://earthobservatory.nasa.gov/images/92598/the-abyss-of-time

[earthstory]

Double rainbow above Siccar Point and Hutton’s unconformity, Scotland!

[earthstory]

Unconformities

A while back we wrote about one of the founding fathers of Geology, eighteenth century Scottish scientist, James Hutton. The concepts that Hutton developed, of deep time and the underlying constancy of physical laws and processes, came from careful observations of the outcrops around him. Some of the most famous are Hutton's 'unconformities'. At a number of places across Scotland, Hutton identified that the rock record revealed gaps in time, with much older rocks directly overlain by younger rocks that must have been deposited many millions of years later. This demonstrated to him the scale of geological time, and how it can be identified in the geological landscape.

The key to the gap in time came from the geometric relations that Hutton observed. The clearest example is at Siccar Point, on the east coast of Scotland, near Edinburgh. Here, Devonian sandstones, deposited 345 million years ago on the arid landscape of the Euramerican supercontinent lie in almost horizontal beds, dipping shallowly out to the current-day sea. But the rocks directly beneath lie with their bedding near vertical. They were deposited on the floor of a Silurian ocean, 425 million years ago, and must have been tilted through 90˚ since they were deposited. A chunk of time, amounting to around 80 million years, is missing from the rock record. Hutton recognised (qualitatively) that gap and the order of events from the relative geometries of the beds. The Silurian marine sediments had lithified, were then uplifted and tilted, and turned on end. Although he could not say much about the gap in time, it follows that erosion formed a land surface, on which the later Devonian sandstones were deposited. The boundary between the basal conglomerate and the Silurian sediments is the unconformity recognised by Hutton.

James Hutton had recorded similar relations in different rocks a year earlier, in 1787, at Newton Point on the island of Arran, west Scotland. Here once more shallowly dipping red sandstones, formed in an arid terrestrial environment, lie on top of steeply-dipping and cleaved grey rocks. The underlying rocks here go by the name of Dalradian, after that of an ancient native tribe. Low-grade metasediments, they were deposited from a continental shelf into a late Precambrian ocean and have subsequently undergone regional scale deformation. The overlying red sandstone conglomerate belongs to the late Devonian and early Carboniferous. Indeed, at Newton Point geologists have subsequently identified a Devonian unconformity, the land surface in the late Devonian formed from tilted and eroded Precambrian basement, and a further disconformity. This represents a gap in time, but with no erosive-tectonic disturbance in the sedimentary sequence, before the subsequent lower Carboniferous conglomerates were deposited.

We take students to Newton Point every spring, to discover for themselves the first steps in reading the rocks. Here is part of this year's group, enjoying Hutton's unconformity at the end of a long day in the field.

~SATR

Image: Newton Point, first year field trip.

More here: http://www.geopoem.com/2013/06/unconformities.html — with 張博翔.