Church Micro 11001...Glastonbury Tor EarthCache
Hidden : 5/14/2017
Difficulty:
1.5 out of 5
Terrain:
3.5 out of 5

Size: Size: other (other)

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Geocache Description:


Number 11,001 in the popular Church Micro series is the iconic ruin of St Michael's Church Tower at the summit of Glastonbury Tor in Somerset.

A brief history of St Michael's Church tower
 St Michael's Tower is a second incarnation of a church at the Tor; the first was believed to be made out of timber and stone and was completely destroyed in 1275 (you will find out how). The second church, built in the 1360s, was destroyed as part of the Dissolution of the Monasteries in 1539 under Henry VIII, alongside Glastonbury Abbey. However, the main church tower was kept- the only part still intact- and is what you see today.

Questions
To claim this EarthCache, you must complete the following tasks. Please email or message me the answers via my profile, don't include your answers in your log. Any answers that are drastically wrong or incomplete, or posted logs that reveal answers will be deleted. I own 15+ EarthCaches so receive many emails/messages per day; I respond to all, but there can sometimes be a delay. Feel free to log the cache as soon as you send answers.

1. As you walk up the tor, you should see terraces as noted in the description. Describe their individual size (approx width, length) and give reasons as to how these may have formed.

2. How does the rock that the tower is built of compare with the Blue Lias Stone on the Tor, particularly around the GZ area? (In terms of smoothness, colour, etc.)

3. What physical differences are there in the rock on the outside of the church tower, compared with the inside? Why do you think this is?

4. Aside from being decorative, why do you think the floor of St Michael's church tower is made from slate?

5. Send me the first sentence of the text (either written or photographed) on the plaque inside St Michael's Tower AND tell me what (geological) occurrence caused the loss of the first church at the Tor.


Erosion forming the Tor
 The Tor is part of the Somerset Levels which consists of bands of limestones, sandstones, clays, and other sedimentary rocks. Usually, sedimentary rocks are eroded fairly easily, but in some cases, the lithology (composition of certain rocks) can differ, changing resistance to erosion.

The Tor itself consists of a formation known as Blue Lias, which consists of predominantly the sedimentary limestone (made up of shell fragments alongside calcium carbonate), shale (Made up of mud, clay and other minerals) and marl. The uppermost section of the Tor, with St Michael's Tower itself, is a Early Jurassic formation known as Bridport Sand Formation, which is around 200 million years old and consists of a harder cap of fine-grained sandstones cemented with calcite and dolomite,, which are carbonate minerals. The Bridport Sands formation is very resistant to erosion and has acted as a 'caprock'- protecting the less resistant Blue Lias below. This means that, as the surrounding clay-rich landscape has been eroded away by glacial action, Glastonbury Tor has not, making it rise up on the landscape.


A cross-section of the naturally occurring terraces on the Tor. You should be able to see these for yourself as you walk up the Tor.

Erosion on the Church Tower
 Like many great buildings, the Tor as an isolated structure is made of natural stone so is susceptible to weathering and erosion, particularly as it has been around for centuries. Weathering is the breakup of rock and erosion is the process of removal of the broken-up rock by water or air. Weathering can occur in three main ways:
Physical involves temperature changes; water seeps into small cracks in the rock and then when this freezes, it expands and breaks up the surrounding rock. This can have a cumulative effect through repeated freezing and thawing.
Chemical involves rain that has become acidic due to water reacting to nitrous and sulphur oxides in carbon emissions. Acid rain reacts with the rock to form solutes that can wash away by the rain.
Biological weathering comes from mosses and lichens which attach to the rock and release chemicals which break up the rock.
All three have affected St Michael's church tower to an extent, as you will no doubt see.

Slate has been used on the flooring of the church tower. This is a fine-grained metamorphic rock that composes of metamorphosised volcanic ash and clay, making it very tough.

Footpaths
The footpaths leading to the Tor, and particularly around the tower itself, the footpaths have begun eroding, due to the vast quantities of shoes breaking up rock around the Tor. As a result, visitors are asked to stick to designated footpaths to reduce further erosion.

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For full information on how you can expand the Church Micro series by sadexploration please read the Place your own Church Micro page before you contact him at churchmicro.co.uk

See also the Church Micro Statistics and Home pages for further information about the series.
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Many thanks to the National Trust's Somerset Area Ranger for allowing this EarthCache to be 'placed' here.

Additional Hints (Decrypt)

Ovt puhepu gbjre ng gur gbc bs gur Gbe- lbh pna'g zvff vg! Sbe dhrfgvba 4, gurer znl or n uvag va gur pnpur cntr...

Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)


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