1. Scotland’s geology
Scotland's geology is a fascination and it started about 650 million years ago. Geologically, Scotland formed 650 million years ago at the South Pole as part of Laurentia, the Earth Plate, which later became North America and Greenland. With Ireland together today's Scotland, so an upstream archipelago of the continent. When continental drift began, Laurentia moved north until it was 400 million years ago at the equator (410 - 260 million years), a reason that the sandstone is found in deserts and coral reefs. During the continental migration, the first mountain ranges of the Scottish Highlands (500 million years) are depicted.
At the same time (425 - 320 million years), this archipelago then collided with the later England and Wales (Baltic continental plate), where the Highlands and Southern Uplands have trained. They have only been sanded down to today's standards by erosion. This impact also created a tectonic fault, the Great Glen, which stretches some 100 km from Fort William on the Atlantic to Inverness on the North Sea. This line divides the Scottish Highlands into the Northwest Highlands and the Grampians.
The erosion that shaped Scotland as it still looks today was due to the 5 ice ages. At that time in Scotland up to 2 km thick ice sheets covered the land. Glaciers have literally milled into the land and shaped the typical U-shaped valleys, firths and lochs. The ice, which moves with uncanny power, has also often left scratches on rocks, eroded mountains and volcanoes, or left thousands of boulders on the slopes of the Highlands.
The thaw between and after the ice ages was no less important: The water masses washed away sedimentary rocks and deposits from the volcanoes and mountains, causing further erosion. There is also an interesting phenomenon on the Scottish coasts of that time: the so-called 'raised beaches'. The thaw caused the sea level to rise and the sea formed beaches along the coast. Over time, however, the land also rose - after all, the tons of ice masses had gradually disappeared. The result is flat, beach-like formations and leaching, but far above sea level. (1)
2. Earth-historical witnesses of the county of Aberdeenshire
The largest part of the country consists of crystalline slate, which belongs to the metamorphic rocks of the Eastern Highlands. Into the metamorphic rock eruptive material penetrated, some before, but most after the folding of the layers. The major species of biotite gneiss are represented by epidiorite and hornblende gneiss swelling in Glen Muick and Glen Callater, which were penetrated by multi-folded granite and pegmatite in ducts and lenses.
As metamorphic rock is called rock, which arises from rock of any type (starting rock) due to an increase in ambient pressure or ambient temperature relatively deep in the earth's crust.
The following rocks are among the most important rocks, which are due to a tectonic deformation:
· Gneiss with a high proportion of feldspars (> 20%), main constituent of granite
· Slate, subdivided into 2 subgenera:
o Slates: very fine grain
o Schists: medium to coarse-grained schists with a relatively high degree of metamorphosis
Isolated masses of granite occur at Peterhead and Streaks. Although mostly made up of biotite granite, the later disturbances pass through intermediate layers of diorite, as in the area between Balmoral and Gairn. The granites were mined extensively in Rubislaw, Peterhead and Kemnay.
The glacial deposits, especially in the belt on the coast between Aberdeen and Peterhead, provide significant clues. The ice moved from the upper reaches of Dee and Don eastward, while the mass spreading from the Moray Firth penetrated the low plateau of Buchan, but at times also clearly northward, parallel to the coast, as the red clay deposit north of Aberdeen shows , At a later time, the local glaciers deposited material on this red clay. (2)
3. Creation of granite
Granites are formed by the crystallization of molten rocks (magma) within the earth's crust, usually at a depth of more than two kilometers below the earth's surface.Granite is therefore a deep rock (term: plutonite). Granites are in most cases not made of material of the mantle, but of molten material of the lower crust.
Like all plutonites, granite also solidifies very slowly at greater depths of several kilometers. The dark minerals, which usually have a high density, crystallize first because of their higher melting point. These sink in the still liquid residual melt and collect in the lower part of the magma chamber. Quartz or feldspar, on the other hand, crystallize later or accumulate in the upper part of the magma chamber due to their lower density. This process is called magmatic differentiation. Granite mainly consists of quartz, feldspar (> 20%) and so-called mafic minerals (dark mica).
The contact with the neighboring rock led to "impurities" in the margins of the magma and to a faster cooling of the magma. Frequently, particularly unusual rock varieties and minerals are produced. This leads to colorations that give the granite its color.
In general, granite is medium to coarse grained. It has a homogeneous mineral distribution with often directionless texture and the resulting relatively uniform appearance. The structure of granite is characterized by direct grain structure, the size of the crystals varies usually between one and several millimeters. You can usually see all the crystals with the naked eye. The color spectrum of granites ranges from light gray to bluish, red and yellowish. The type of solidification (crystallization) and environmental influences to which the rock was exposed play just as much a role as the mineral content.
By further movements of the earth's crust and erosion of the overlying rock then passes the solidified granite to the earth's surface. The granite can change significantly due to tectonic or hydrothermal processes. (3)
4. Use of granite from the county of Aberdeenshire
Scotland has a relatively large number of granite intrusions, which differ in their composition and geological age, with different characteristics of stones from different regions, such as the silver-gray granites of Galloway, the deep reds of Ross of Mull and Peterhead and the salmon Rosa from Corrennie in Aberdeenshire.
The city of Aberdeen, known as "Granite City", is built to a large extent from silver gray granite quarries in and around the city. Many quarries served as building material for the region, but were used for export in several areas on a larger scale.
Peterhead Granite, one of the most important granites of Aberdeenshire, was made as a red and blue Peterhead variety that was exported to the UK and abroad in the 19th century. The red variety was better known and was used for ornamental and monumental works, eg. London, Cambridge (St John's College Chapel Columns) and Liverpool (St George's Hall Columns).
The blue Peterhead Granite was used for decorative and decorative work, eg. the base of the fountains at Trafalgar Square and the Prince Albert Mausoleum. Peterhead Granite is still mined in the Stirlinghill and Longhaven quarries, where it is mostly minced for aggregates. (4)
5. Log conditions for the EarthCache
To log this EarthCache, please answer the questions below and send us your answers via Message Centre or via e-mail. After you have sent us the answers, you can log EarthCache online. Please do not post the answers in your online log. Your log entry will be deleted otherwise. If something is wrong with your answers, we will contact you.
All questions can be answered on the basis of the listing and the visit on site. Special expertise is not necessary to answer the questions.
Questions:
Go to Waypoint 1. In front of the gate, a small path turns right along the wall. Follow the path for about 180m along the wall. The terrain behind the gate is private property and does not need to be entered.
1 ) When looking at the rocks, you can clearly see that they are coming to the surface at different angles. What is the cause why the rocks are comming diagonally to the surface?
2 ) Take a closer look at the granite. Describe the present color of the granite.
3 ) What is the cause of the granite’s color found here?
4 ) The last task as a logging requirement for this EarthCache is a photo that documents your visit on site. Please take a photo of you or a personal object, so that the lighthouse can be seen in the background. Please attach it to your log entry and do not send it as a message.
Online logs without a photo will be deleted.
*
Since June 10, 2019, Groundspeak has changed the logging conditions for EarthCaches to allow a photo to be re-registered as proof of EarthCache's visit.
(see https://www.geocaching.com/help/index.php?pg=kb.chapter&id=51&pgid=296)
And now we wish happy caching and a lot of fun in this impressive environment.
The use of the listing text without prior permission, even in extracts, as well as the photos is expressly objected.
Photos: Copyright by Tomcat909, Tintenklexx
Literature:
(4) https://www.buildingconservation.com/articles/rockofages/rockofages.htm
(3) https://en.wikipedia.org/wiki/Granite and https://de.m.wikipedia.org/wiki/Granit
(2) https://en.wikipedia.org/wiki/Aberdeenshire and https://de.m.wikipedia.org/wiki/Aberdeenshire
(1) https://schottlandinfos.de/schottische-geologie
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