At this Office park location is a small sculpture containing two types of rock. There are three main ways that rock forms and two of them are shown here.
Igneous rocks are formed when melted rock, called magma cools and forms a solid again. Its physical properties depend on how quickly it cooled. As it cooled, crystals formed which tend to be of similar size. Examples of Igneous rocks are:
Granite – slowly cooled magma that has small even sized grains
Pumice – which is very light as it cooled quickly in the air and trapped pockets of air in its structure
Sedimentary rocks are formed when small pieces of rock are deposited on the bottom of streams, lakes and oceans. More layers are deposited and over time the rocks at the bottom become compressed and become rocks. Examples are:
Limestone - formed from calcite deposited under seas and from sea shell
Sandstone – formed from small grains of quartz and feldspar.
Metamorphic rocks are formed when heat and pressure within the earth cause one type of rock to turn ‘metamorph’ into another type. This is characterised by flattened grain structures which mean that the rock is weaker in one plane than in another.
Examples are (with increasing temperature and pressure):
Slates - based on clays but weak in one plane
Schists – contains flakes of mica so tend to be shiny
Gneiss – tend to have coloured bands as the different minerals crystalise seperatly
In order to claim this cache you must answer the questions below and send the answers to me.
- Describe the appearance of the rocks that make up the sculpture. There are two different rocks used in the sculpture. One forms the border and one the floor. Identify what each is called.
- Which types of rock are they and why do you think that?
Unfortunately the sculpture has had the vertical elements removed and is not as striking as it was. I have revised the questions.
This cache is inspired by Earthcaches set be Loony Londo who has set some most unlikely Earthcaches in London that have given me many lunchtimes of happy caching.
Congratulations to ReggieCat for FTF.
slight increase in diffficulty rating due to recent answers
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