Salisbury Plain is a chalk plateau in central southern England covering 300 square miles (780 km2). It is part of a system of chalk downlands throughout eastern and southern England, formed by the rocks of the Chalk Group and largely lies within the county of Wiltshire, with a little in Hampshire. The plain is famous for its rich archaeology, including Stonehenge, one of England's best known landmarks. The real Stonehenge is made up of two main rock types, The Blue stones, an igneous rock from Craig Rhos-y-Felin, near Pont Saeson in north Pembrokeshire and The Sarsens a sandstone from the plains close to Marlborough
Earth cache (or rock) lesson Here are descriptions of three types of rock mentioned above.
Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates (coccoliths) shed from micro-organisms called coccolithophores. It is common to find chert or flint nodules embedded in chalk. Chalk can also refer to other compounds including magnesium silicate and calcium sulphate.
Sandstone is a type of stone made as animals and small rock particles fall to the bottom of the ocean. It can be coarse grain, where the particles are as big as grains of rice (and sometimes bigger) to very fine mudstones, where the particles are microscopic and can’t actually be seen with the naked eye. Sandstone can be a variety of colours depending on the percentage of animal material is included and the type of rock that has contributed to the particles. Most sandstone is yellow in colour but it can be reddish and of a grey hue too. One confusing aspect of sandstone is that, as it is left out in the open, it all tends to go a greyish dirty colour, this is due to pollution. In the mid part of the 20th Century most sandstone in industrial areas was black due to the amount of soot in the air from coal fires. Today most pollution is from motor vehicles and this turns sandstone the greyish colour. This type of stone is very commonly used to sculptures and standing stones because of its resistance to weather and its ability to ‘hold’ a carved shape for many years.
Igneous rock is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either chalk or sedimentary rocks. The rock can feel smooth since it has been tempered by the heat it has been subjected to and weathering has little effect on the surface. It is often foliated (composed of layers of sheet-like planar structures), which means it can fracture under weathering, leaving deep fissures in the rock. The foliations are characterized by alternating darker and lighter coloured bands, called gneissic banding". The banding is developed under high temperature and pressure conditions. The minerals are arranged into layers which appear to be bands, when the rock is broken and viewed from the side (in cross section). This is because of a different composition of each layer, or band, called compositional banding.
To log a find, your task (should you choose to accept it), is to answer the three questions below and post a picture of yourself or your GPS at the stone circle. (The picture bit is optional)
Please message me your answers and feel free to log your find at the same time.
1) Go and have a good feel or hug the stones and tell me what they feel like.
2) Read the three descriptions of types of stone above and tell me which rock type were used to make this stone circle.
3) Tell me the height of the smallest and largest stones.
Finally thanks to 'The Wooks' who put me onto the English heritage website which confirmed that the stone circle was built in 1998, when it was at the edge of a new housing development at Butterfield Down, Amesbury . Today as you can see it is very much in the heart of the estate but is still in its untouched state.
As always, stand and feel the power of the circle and thanks for visiting the cache.