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Geological Dartmoor.

A cache by Wadders Send Message to Owner Message this owner
Hidden : 07/07/2011
1.5 out of 5
2.5 out of 5

Size: Size: other (other)

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Geocache Description:

This is an Earthcache, NO box exists, NO log to sign but to claim it as a find you MUST answer some questions and email me the answers, if you do not follow these instructions I WILL DELETE YOUR LOG!

Dartmoor is a stunningly beautiful area of moorland accented with wooded valleys and wind swept Tors (the old celtic word for "tower"). A wide-open expanse covering 369 square miles (953 sq. km.), the area features some of the wildest and bleakest country in England.

How a Tor is formed; Firstly you have a normal hilly landscape; Then erosion takes place exposing the harder granite beneath leaving it exposed to be weathered into tors.

Dartmoor has a varied and vast amount of different geology as can be seen from the following chart.

Granite The name granite comes from the Latin granum, a grain. Granites are composed of fairly large crystals and have an irregular granular or granitoid texture. Granite is a group name for a family of plutonic or deep-seated acidic igneous rocks. Dartmoor granite is made up mainly of quartz (glassy, grey/white crystals of silicon dioxide), felspar (particularly orthoclase - potassium aluminum silicate: but also plagioclase) and biotite, a type of mica - a complex hydrated silicate of aluminum and potassium with iron, magnesium and fluorine. Dartmoor granite is also characterized by a relatively high proportion of tourmaline, which is blacker than biotite and distinguishable by its finely grooved surface. Some geologists have identified three major types of Dartmoor granite - the contact granite contaminated by minerals from the surrounding rocks; the tor granite which contains the large megacrysts typical of many of the tors, and the finer grained blue granite.

An example of Megacrysts

To log this cache;
Please email me through my profile the answers to the following questions, if i do not receive the answers from you I WILL delete your log.....Simples :-)
1/ Please measure the length & width in Millimeters please, of three of the larger crystals on the NW face of Haytor where the arrow points @ N50 34.820 W003 45.328
A/ Optional photo of the above (not in the log please)

2/ Please explain why you think that these large crystals cooled quicker or slower than the smaller crystals?
3/ Optional photo of yourself with gps at Haytor (can be on the log)
4/ The Dartmoor Granite is connected at depth with the other granite masses of Cornwall, This forms an enormous granite intrusion known as what?
5/ Temperature approaching 1000° C, altered surrounding rocks for several hundred meters beyond the margin, forming a metamorphic rock known as what?
6/ What initially caused the cracks/joints in the tor?

Please email me through my profile the answers to the above questions and await my response BEFORE LOGGING, if i do not receive the answers from you I WILL delete your log.....Simples :-)

My thanks to Dartmoor National Park for permission in setting this cache. References used;
Devon county council web site

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