Empedocles (c.494 – c. 434 BC) was a Greek pre-Socratic philosopher who suggested that four ultimate 'roots' made all the structures in the world, namely: earth, air, fire and water. Plato later referred to these 'roots' as 'elements', often known as 'classical elements'. These are clearly to be differentiated though from our current scientific understanding of chemical elements and the Periodic Table.
This mini-series of caches is based around the four Empedoclesian 'roots', with each one relating to either earth, air, fire or water.
This is an EarthCache and so there is no physical container to find at GZ. Instead, you will need to make careful observations of the traditional rough-stone walling on the facade of the recently constructed Lakeside conference centre (at the posted co-ordinates).
Rock classifications
Igneous rocks form when molten rock (magma if underground, or as lava if above ground) cools and solidifies. A particular feature of igneous rock is the randomly arranged, interlocking crystals. Depending on the rate of cooling, igneous rocks can have differing crystal sizes and hence properties. Magma that cools slowly will form an igneous rock with large-sized crystals whereas lava that cools quickly will form an igneous rock with small-sized crystals. Examples of igneous rock include granites, basalts, gabbro, obsidian and pummice.
Sedimentary rocks are formed when existing rock is weathered and eroded which creates small grains and fine particles that are transported by wind, water, ice or gravity. The grains and particles are then deposited to form layers of sediment which build up and become compressed over millions of years to form sedimentary rock. During the transportation process, grains and particles from different rock sources can become overlaid, and along with differing chemical elements and processes, this gives rise to different coloured layers or strata. Examples of sedimentary rocks include limestone, sandstone, mudstone, shale, chalk and coal. These rocks are often important for the study of fossils (Palaeontology), as animals and plants can become trapped in the layers of deposition and fossilised as the rock forms.
Metamorphic rocks are formed when existing rocks undergo further physical and chemical transformations when placed under great heat and pressure. Examples of metamorphic rocks include marble, slate, gneiss (pronounced ‘nice’) and schist. Metamorphic rocks can feature contorted bands of minerals known as foliation.
Questions to answer
- Look closely at the rocks in the wall and describe their surface texture.
- Describe the different colours present in the rocks. What causes the different colours?
- Some of the rocks have clear horizontal features within them of different coloured rock. What causes these horizontal features?
- Based on your responses to the previous questions, and the descriptions above, what is the classification and type of rock?
Please send your answers (via either the message centre or email) before logging your visit.
Please do not post any photos or descriptions of the rock specimens or features relating to this EarthCache in your log.
Many thanks to the reviewer, GeoawareUK3, for their helpful feedback and advice during the review process.
