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Orpen Balancing Rocks EarthCache

Hidden : 7/20/2009
Difficulty:
1.5 out of 5
Terrain:
1 out of 5

Size: Size:   other (other)

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Geocache Description:

This EarthCache will be forming a part of a series in the Kruger National Park researched by cincol and Carbon Hunter during the winter of 2009.

The Orpen Balancing Rocks can be found to the North of Skukuza on the H-2 Route to Tsokwane. There are a number of similar rock formations nearby with the most notable being the Kruger Tablets site about 2km north, but the published co-ordinates will take you to a specific spot where you can observe the rocks from very close up without having to alight from your vehicle at all. Remember that it is neither SAFE nor LEGAL to get out of your vehicle at any point in the Park unless specifically authorized to do so.

These koppies (outcrops) represent some of the most prominent of a number of Archaean granite tors (also commonly called “castle koppies”) developed in the eastern parts of the ±3000 million year old granite domes that can be seen at many points in the Kruger National Park. This dome stretches throughout the central part of the Park [from south west of Skukuza in the Pretoriouskop region] with this area being towards the northern limit of the dome. The tors in this part vary in both composition and texture. But generally consist of medium to coarse grained homogenous granodiorites and adamellites, as well as banded gneisses and migmatites. In some of the tors the granitic rocks contain large feldspar crystals (this is clearly visible in some of the rocks scattered around the park near the co ords) in a finer grained matrix – these are reffered to as porphyritic granites. Tors similar to Orpen Rocks are extensively developed in the Archaean granites of Zimbabwe [think of the balancing rocks of the Matopos where Cecil John Rhodes is buried and other outcrops around Bulawayo and Harare], other parts of Mpumalanga and Swaziland – of which the Orpen Rocks are part of; and formed mainly by differential weathering of the faulted, fractured and jointed granites.

In order to qualify to log this cache, you need to answer the following questions and e-mail the cache owner at cincolcc(at)gmail.com Any logs not accompanied by an e-mail will be deleted.

1) Take a photo of you and your GPSr at this spot with the plague on the granite outcrop visible and include in your log - optional.

2) Look at the exposed granite. Describe from the “crystal” or grain size whether this rock cooled quickly (like a dolomite or obsidian with small grains) or more slowly to produce larger grains.

3) Describe what the granite looks like (including texture and colours).

4) Explain how the rocks may have ended up “balancing” on each other.

5) What is the date that is shown on the plaque at the location?

FTF goes to - De Kokopelli's

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