This earthcache will show you the difference in appearance between serpentinous marble (a metamorphic rock) and Larvikite (an igneous rock).
The Anchor Line building entrance pillars are of a pale green serpentinous marble with the base of the columns composed of a darker rock – Larvikite.
Metamorphic rocks are those which have been altered from their original state, either by heat, pressure, or very often, both. The altered state often results in new crystals, textures and foliation forming within the rock. Metamorphic rocks were originally igneous or sedimentary, before being subjected to high temperatures and pressures: when limestone is metamorphosed, it results in marble.
Serpentine is often called 'green marble', even although its geological makeup is different from traditional marble. Whereas marble is calcite based, serpentine has a magnesium-silicate base. The stone gets its name from the figurative 'snake scales' that become apparent when water comes into contact with the stone.
Igneous rocks form when molten rock originating from deep within the earth’s crust cools (either below the surface as an intrusion e.g. granite, or above the surface as an extrusion e.g. basalt lava). The resulting igneous rock is composed of interlocking crystals, the size of which depends on the time taken for the molten rock to cool.
Look for the pillar which has the brass sign 'Anchor Bar'.
Examine the pillar and base, then answer the following questions:
Q1. Describe the colour and texture of the pillar.
Q2. Are there any obvious markings on the pillar?
Q3. Describe the colour and texture of the base.
Q4. Which has the more obvious crystals - the pillar or base? Why do you think this is?
Q5. Please provide a photo of yourself or a personal item near GZ (without giving away the answers).
Answers to questions 1-4 should be sent by the message centre or email. Please DO NOT include the answers in your log.
Please send your answers BEFORE logging the cache. You do not need to wait for a reply, but if there is a problem, we will let you know.
ANY LOGS ENTERED WITHOUT ANSWERS BEING SENT WITHIN TWO WEEKS WILL BE DELETED.
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