Unconforming to Tradition EarthCache
Unconforming to Tradition
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This Earthcache takes you to the town where James Hutton (an 18th century Geologist, Chemist and Naturalist) in 1787, had an insight into the true age of the Earth. Just South of this location, (now unfortunately on private land and unstable) James Hutton observed beds of vertical Greywacke overlain by horizontal beds of Sandstone. From his previous observations on sedimentation, he deduced that the greywacke must have been laid down over a period of years, the bedding plane subject to earth movements to cause the beds to lie vertical, the top surface was subject to erosion and then at a later time new layers of sandstone were deposited on the top. He called this an Unconformity as there had been a period of time where there had been a gap in the formation of rocks, the junction between the two being the Plane of Unconformity. Over a period of years and observations at many sites he came to the conclusion that The Earth was countless of millions of years old, and had undergone many episodes of lifting, erosion, tilting and deposition.
Sedimentary Rocks
Here we have an example of sedimentary rocks. Sedimentary rocks are formed by the deposition of material over time. This material maybe clastic as a result of weathering and erosion of existing rocks into smaller fragments (eg Sandstone), chemical, ions carried in solution and then deposited when conditions change (eg Oolitic Limestone) or biological, organic material such as shells or trees (eg Coal) This sediment is usually laid down in layers which then get compressed over time to create solid rock. (Diagenesis)
Sandstone
Sandstone is a sedimentary rock composed of 0.0625 to 2mm fragments of mineral particles or rock cemented together. Usually the mineral fragments are quartz or feldspar as these are more resistant to erosion. The cement may be silt or clay. It is a useful material for buildings as it can be easily cut into a variety of shapes and relatively weather resistant.
Greywacke
Greywacke is another form of sandstone but the rock fragments (clasts) are more irregular and poorly sorted, There is a lot more clay matrix. They are formed underwater by avalanches of unsorted material being churned by the ocean current to form turbidites. They are thought to be usually formed at the edge of continental shelves. A common use for greywacke is as aggregate.
At GZ the town council has erected a sculpture to represent the Unconformitiy. This Earthcache requires you to visit this sculpture and make some observations. A nearby notice board may also help your answers.
Now, to claim the Earthcache, you need to answer some questions, which you need to email or message via the message centre to the CO, please do not put your answers (or any great clanging hints!) in your logs, or Iโll have to delete them. Feel free to log the cache as found as soon as you have sent the email.
So, to your tasks
1. What are the ages of the Greywacke layer and the Sandstone layer. How long is the period of time represented by the plane of unconformity.
2. Describe the colour and texture of both the Greywacke and Sandstone.
3. From your observation at GZ, which stone is the Abbey most likely made from?
4. To prove you have visited the site which two words are in italics on the bench just North of GZ?
5. As always, photos are nice, but not essential โ but please avoid leaving spoilers!
Enjoy the nearby refreshments too. It is one of our favourite stopping off points when we travel North this way.
Additional Hints
(Decrypt)
Ernq gur vasb obneq!
Treasures
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