This earthcache can be completed at the coordinates with the information on the cache page, but you may find it helpful to visit the "Restless Earth" Gallery at the National Museum of Scotland as well. An event to celebrate the tenth anniversary of Earthcaching was held there on 10 January 2014. The Gallery is on Level 3 at the east end of the museum. The National Museum of Scotland is open daily between 10am and 5pm and has free admission.
Geologists categorise rocks into three types sedimentary, igneous and metamorphic.
Examples of each of these can be seen in the NMS Gallery - check out the different types of sedimentary rock, including the one with the fossil shells, the beautiful mineral formations from the igneous rocks, and the really neat folds and wiggles in the metamorphic rocks
Sedimentary rocks form when small weathered pieces of rock and animal remains are swept downstream and eventually settle on the seabed. As the sediment deposition builds up in horizontal layers the pressure from above cements the minerals together and turns them into rock.
Igneous Rocks are crystalline rocks formed from solidified magma and are formed either by volcanoes where lava and ash form extrusive rocks such as basalt and tuff, or as intrusive rocks when magma gets trapped in underground pockets. Examples of this type of igneous rock include granite. Rocks which cool more slowly generally allow larger crystals to form.
The final rock type, Metamorphic, form from other rocks that are changed because of heat or pressure. Earth movements or proximity to lava can cause rocks to be heated, deeply buried or squeezed. When some rocks are heated and put under great pressure, the minerals they contain are changed chemically rather than melting, forming metamorphic rocks.
Looking towards the Library at the coordinates you can see three different rocks - two light coloured ones on the ramp and a darker one on the building itself.
Using what you have learned from the cache page, the NMS gallery or elsewhere, please
- state what type of rock each one is (e.g. igneous, sedimentary or metamorphic).
- What distinguishes the two lighter coloured rocks?
- One rock has visible crystals in it - how large are they on average and how quickly do you think this rock cooled?
- From considering the building stones used in the older buildings in the area, or otherwise, can you identify which of these rocks is local? Please give a reason for your answer.
Earthcachers may also be interesting in visiting the gravesite of James Hutton, "Father of modern geology" in the nearby Greyfriars Kirkyard, close to the second waypoint.
This cache was also part of the Edinburgh Earthcache weekend and geocoins are available here