Turnbull Clan Association


geological map 1The peoples and products, the rulers and traditions of our homeland have oft been discussed in these articles. Today however I shall ramble on about the rock that is Scotland.Where did it come from? How long has Scotland been around? Things like that…
Long, long ago and far far away… No wait, different story… Reboot… Beneath the beauty of Scotland’s landscape, under the cities lochs and rivers lies the stone and soil backbone that is the foundation of the civilization to which we are devoted. For we who live here in the twenty first century, especially for us Turnbulls, the history of Scotland starts with and around Robert the Bruce and his battle against England. The truth is that those events are very recent given the tremendous age of the Earth.

The concept of ‘deep time’ was developed in the 18th century by Scottish geologist and father of modern geology, James Hutton (1726-1797). His conjecture was that the geologic time scale is overwhelmingly huge because this planet is so very old. Hutton noted the significant difference between the layers of stone at Siccar Point east of Edinburgh. In 1788, Hutton, along with fellow scientist John Playfair traveled along the coast of Berwickshire in south east Scotland. Here they found dramatically contrasting rock formations. Hutton called his discovery “a beautiful picture of this junction washed bare by the sea.” He proclaimed his find proved that the Earth is vastly older that previously speculated. Hutton’s Unconformity is simply a site where two layers of stone have been thrust together. The upper layer eons younger that the lower. We can see these layers revealing that the sedimentation was not a continuous process. Basically this means that the older layer was exposed to the elements and had eroded before the younger layer was deposited on top of it, where, over time, it petrifies into solid stone.
geological migration 3Based on radiometric* age dating, this planet Earth is said to be some 4.5+ billion years old. That is not to say that Scotland is so old, whatever the younger generation may think of the elder. Humans occupied the territory that would
become Scotland some 10,000 years ago at the end of the Devensian glaciation, the last ice age. Prior to the coming of man, Scotland went through a great many alterations before it became the most beautiful place on Earth. Stones have been found in the Lewis, Harris and North West Sutherland regions that date back three billion years. Seeing these rocks can be awe inspiring when you think of the tremendous age of our planet. Eons of volcanic activity, earthquakes and climate change have gradually eroded the terra firma that we love today.
It would be impossible for an amateur such as I to cover the geological history in a short article but suffice it to say that Scotland began its history in the region that is now in the Antarctic. The British Isles began as part of an ancient continent called Laurentia that existed in the southern hemisphere. Experts proclaim that this long ago continent included North America and Greenland as well as the British Isles. Over the last 500 million years though, Laurentia broke up and migrated north to form the geography that presently exists. In another 500 million years who knows where Scotland will be…
geological siccar 2The portion of Great Britain that is Scotland is made up of five distinct geological sections: the Lewisian gneiss and Torridonian of the North West; the Moine rocks of the Central and Northern Highlands west of the Great Glen Fault; the Moine and Dalradian of the Central and Grampian Highlands; the Midland Valley and the Southern Uplands. Large faults, some of which are still identifiable in the landscape, separate these areas and are known as the Moine Thrust in the north-west, the Great Glen Fault, the Highland Boundary Fault and the Southern Upland Fault.
Some 410 million years ago the islands that became Great Britain joined together as the ocean separating them slowly closed thus forming the Southern Uplands, which is now the Border Country. During the 60 million (give or take a few million) years that it took for Scotland to travel across the globe she experienced all forms of climate from arctic cold to dessert heat. The climate fluctuations along with volcanic activities at times made the land uninhabitable.
There is however, evidence that about 400 million years ago conditions existed that in the Rhynie area of Aberdeenshire, silica rich hot springs preserved some primitive plants along with the earliest known insects in rocks known as Rhynie Chert;a sedimentary rock that contains fossils. This is also evidence that dinosaurs roamed the Scottish landscape. (Can you say Nessie?) In the Jurassic and Cretaceous periods Scotland was for the most part either submerged under shallow tropical seas or very hilly but would have supported the animals of the day. Dinosaur fossils have been found on the Isle of Skye. Seven species have been identified so far.
The most ancient stones in Scotland, located in the Outer Hebrides, are also the oldest stones in Europe. Examples can be seen in Lewis at Callanish where they were used as the Standing Stones. They can also be found on the mainland in a thin strip of the Northwest coast. The stones are buried deeply under much younger sandstone and limestone that are only about one billion years old and are the oldest sedimentary rocks in Scotland.
geological rhynie 4Scotland’s geological makeup is quite varied for a land as relatively small as it is. There are three main geographical subdivisions: The Highlands and Islands, northwest of the Highland Boundary fault**; the Central Lowlands, a rift valley made up of Paleozoic formations; and the Southern Uplands south of the Southern Uplands Fault***. The Southern Uplands are mainly Silurian deposits from 443 ± 1.5 million years ago.
Scotland’s (the whole planet actually) history can be plotted on a time scale that covers the eons starting with the Precambrian period (4,560 to a mere 542 million years ago) up to the present Quaternary period that started just yesterday (1.6 million years ago) and runs to the present. For more information regarding the time scale visit the Scottish Geology website at: http://www.scottishgeology.com/geology/geological_time_scale/time_scale.html
Eons and Epochs, eras and periods, millennium… It would be impossible to cover all of Scotland’s geological history in a single article. There are many books on the subject and the websites are countless. Maybe I’ll do a future story all about James Hutton.
*Radiometric dating (often called radioactive dating) is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates. It is the principal source of information about the absolute age of rocks and other geological features, including the age of the Earth itself, and can be used to date a wide range of natural and man-made materials. .
** The Highland Boundary Fault is a geological fault that traverses Scotland from Arran and Helensburgh on the west coast to Stonehaven in the east. It separates two distinctly different physiographic regions: the Highlands from the Lowlands, but in most places it is only recognizable as a change in topography. http://en.wikipedia.org/wiki/Highland_Boundary_Fault
*** The Southern Uplands Fault (or occasionally Southern Upland Fault) is a fault in Scotland that runs from Girvan (or more specifically from the Rhins of Galloway) to Dunbar on the East coast. It marks the southern boundary of the Scottish Midland Valley. http://en.wikipedia.org/wiki/Southern_Uplands_Fault

geological map detail 6

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