War Memorial # 2391 ~ Coombe Hill EarthCache

Coombe Hill Monument, Second Boar War.

Coombe Hill Monument is one of the first and largest examples of a war memorial erected to honour the names of individual men who fell whilst fighting for their country. At 850 feet (260 m) above sea level, it sits on one of the highest and most striking spurs of the Chilterns, commanding a wide view of the Vale of Aylesbury. On a clear day, it can be seen from the Berkshire Downs and the Cotswolds to the west. The view overlooks Chequers, the country home of the Prime Minister.

The monument was erected in 1904, by public subscription, in memory of 148 men from Buckinghamshire who died during the Second Boar War. Coombe Hill Monument was almost totally destroyed by lightning in 1938 and was rebuilt in the same year. The original bronze plaque and decorations were stolen in 1972 and replaced with a stone plaque and iron flag. The new stone plaque was also inscribed with the additional names of nine men believed to have been missing on the original. The monument was again badly damaged by a lightning strike in the early 1990s and spent several months in repair. It is now equipped with conductors to prevent this from happening again.

Logging Requirements (Questions to Answer)

Compulsory tasks in order to log a find against this EarthCache, you will need to visit GZ and make some observations and then answer some questions and send answers to me via my Geocaching profile or through the Messenger Centre.

You won't need a magnifying glass or anything like that to complete the earthcache but if you have one, or ideally a hand lens or even a magnifying app on your smartphone, you'll be able to see the makeup of the rock in much greater detail.

Due to extensive restoration two types of granite can be observed, one contains large phenocrysts.

1) Look at the contrasting features of the granite above and bellow the red line, please tell me which one cooled slowly, give your reasoning for your answer?

2) Below the word 'OCTOBER' on the lower plaque. You can find the largest phenocrysts. Please describe it's size, shape, and colour.

3) Are the phenocrysts anhedral or euhedral - please explain why you think this?

4) Also include in your log a photograph of you, your GPS or another identifiable item near GZ, taking care not to include anything in the photo that may give away your answers.

Granite

Granite is a common type of igneous rock. Igneous rock  is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava. Igneous rock may form with or without crystallisation either below the surface as intrusive (plutonic) rocks or on the surface as  extrusive (volcanic) rocks. 

It is composed mainly of three minerals: quartz, feldspar, and mica. These crystals form when magma, rich in dissolved minerals, cools slowly underground. As the magma cools, the minerals within it start to crystallise. However when the cooling process is gradual, the crystals have time to grow larger than the surrounding minerals creating phenocrysts, they contrast sharply in size with the enclosing groundmass; this implies a size ratio of at least about 5:1.

Phenocrysts provide valuable information about the conditions under which the rock formed and the history of volcanic activity in the area. Euhedral phenocrysts are characterised by well-defined crystal faces and sharp edges, indicating that they had enough space to grow freely within the magma before it solidified. On the other hand, anhedral phenocrysts lack distinct crystal faces and appear irregular in shape, suggesting that they formed in a confined space or in a rapidly cooling environment where crystal growth was hindered.

Permission to place this earthcache was given by Matt Livarski-Bond, National Trust Area Ranger.