Gneiss Landscapes – TumbleStone

In 2003 I had visited Stonehenge while on a camper-van holiday in the UK. I found it intriguing and mysterious. I also visited the much larger and quite different stone circle at Avebury, a few kilometres to the north, and was again struck by its ancient mystery. Since then, I have read a lot about stone circles, megaliths and standing stones, feeling drawn to them. I read about the Standing Stones of Callanish (sometimes referred to as the “Calanais” Stones) on the Isle of Lewis in northern Scotland and they seemed to me to be among the most interesting and intriguing, and about twelve years ago I bought a photo of them to hang in my hallway at home.

On Friday 27 May 2017 I flew into Stornoway, the main town on the Isle of Lewis in the Outer Hebrides. I was on my way to spend a few weeks with my wife who was working with dairy farmers in Devon, and I took the opportunity to visit Lewis for three days with the main aim of seeing the Standing Stones of Callanish firsthand. The following morning, I met with Dave Godwin, a local archaeologist, who I had hired for the day to show me around the Island and to fill me in on its history, culture and environment. Later that afternoon he introduced me to the Callanish Stones.

That evening, and the next couple of nights, I stayed with John Angus Morrison at Taigh Solus, an excellent B and B accommodation in the village of Arnol. John was a very good host and looked after me well, and we had some great conversations about life, the universe and everything. I returned to the Stones the next two days and also spent time at other megalithic sites nearby. I took photos from an array of different distances and angles. The weather was cold and partly-cloudy, and at times there were up to 15 people visiting – Callanish is easily accessible, anyone being able to walk among the Stones and touch them.

These Standing Stones pre-date Stonehenge by about 500 years, having been erected about 5,000 years ago. They were an important place for ritual activity for at least 2,000 years. It is generally believed that Callanish functioned as an astronomical calendar associated with the moon and that it accurately marked the 18.61 year cycle of maximum lunar declination. Every 18.61 years, the moon skims especially low over the southern hills on the horizon, skimming the tops of the Stones.

There are about 50 stones at the main site at Callanish. Thirteen of them (with an average height of three metres) are set in a circle of just over 11 metres in diameter, with a five-metre high monolith, probably weighing about seven tonnes, near the middle (see aerial photo below). Five rows of standing stones connect to this circle – two long rows of stones (nine on one side and ten on the other) run almost parallel to each other for about 80 metres from the stone circle to the north-northeast, forming a kind of avenue; shorter rows of stones run to the west-southwest, south and east-northeast. These stones are between about two-and-a-half and three-and-a-half metres high. Within the stone circle is a chambered tomb in front of the central stone.

SC1023422 — Callanish Standing Stones from the air (Source: http://www.dayofarchaeology.com/tag/callanish-stones)

Two YouTube clips of the Stones:

It is argued by many that the Standing Stones are a complex and sophisticated celestial observatory, many aspects of which are now lost to us. How the Stones are aligned, their shapes, their heights, the shadows they throw, how they relate to the sun and moon and stars, and how they relate to the surrounding landscape, are thought to be significant. One scholarly study showing Callanish was constructed specifically in line with the movements of the sun and moon, 5,000 years ago, is Gail Higginbottom and Roger Clay (2016), “Origins of standing stone astronomy in Britain: New quantitative techniques for the study of archaeoastronomy”. These researchers also discovered a complex relationship between the alignment of the stones, the surrounding landscape and horizon. A University of Adelaide press release quotes Dr Higginbottom: “This research is finally proof that the ancient Britons connected the Earth to the sky with their earliest standing stones, and that this practice continued in the same way for 2,000 years.” Examining a number of standing stone sites in detail, it was found that about half the sites were surrounded by one landscape pattern and the other half by the complete reverse. “These chosen surroundings would have influenced the way the sun and moon were seen, particularly in the timing of their rising and setting at special times, like when the moon appears at its most northerly position on the horizon, which only happens every 18.6 years,” Dr Higginbottom stated. “For example, at 50% of the sites, the northern horizon is relatively higher and closer than the southern and the summer solstice Sun rises out of the highest peak in the north. At the other 50% of sites, the southern horizon is higher and closer than the northern, with the winter solstice Sun rising out of these highest horizons. These people chose to erect these great stones very precisely within the landscape and in relation to the astronomy they knew. They invested a tremendous amount of effort and work to do so. It tells us about their strong connection with their environment, and how important it must have been to them, for their culture and for their culture’s survival.”

A small demonstration of one aspect of how the summer solstice is recorded on the Callanish Stones is on YouTube:

The stones are local Lewisian gneiss, the oldest rock in the British Isles. This rock is igneous in origin but has been subject to significant metamorphic forces. White quartz and dark hornblende crystals can be seen in the stones. The word “gneiss” (pronounced “nice”) comes from the Middle High German verb “gneist”, meaning “to sparkle”, as the rock glitters.

Gneiss is an ancient and very hard rock. It is medium to coarse grained. It has been subject to high pressure and heat, so much so that the minerals in it separate out and form distinct but often discontinuous bands. Light-coloured bands are mainly formed of quartz and feldspar while the darker bands consist of minerals like amphibole (hornblende), pyroxene and biotite mica. Unlike slate and schist, gneiss does not preferentially break along planes of foliation because less than 50% of the minerals formed during the metamorphism are aligned in thin layers. It is because of the coarseness of the foliation that the layers do not have a constant thickness, and are discontinuous.

gneiss2

Gneisses form deep in the Earth in subduction zones or under the roots of fold mountains. They are bought to the surface only by massive tectonic movements or slow erosion. Gneiss from western Greenland comprises the oldest crustal rocks known (more than 3.5 billion years old, about two-thirds the age of the Earth). Lewisian gneiss is about three billion years old, the oldest rocks to be found in Britain. It is thought that the original rock was probably sandstones and limestone or igneous rocks like basalt and granite, which was then subject to metamorphism. About two million years ago the Ice Age came to Lewis. The movement then retreat of large glaciers formed the smooth rocky landscape of Lewis. After the main ice melt 12,000 years ago, the sea level rose, flooding river valleys and lower ground and creating the lochs and drowned valleys of the Isle. As the climate improved, soil formed and plants and woodland returned. Peat developed on the poorly drained ground and extended upwards and outwards to cover large tracts of land.

The Callanish Stones are thought to have been quarried about one to two kilometres from their present site. They are very good examples of Lewisian gneiss.