Geoglyphs are one of the lingering mysteries of the archaeological world, but what is their value in the modern world?

What is a Geoglyph?

Lets starts with a definition, so we are all on the same page, according to the Cambridge Dictionary a geoglyph is: A large design on the earth’s surface made by people removing or placing soil, sands, stones etc.

They occur across the world from Peru to the UK to Australia. Depict everything from people to geometric designs or straight lines miles long. They occur in inhospitable dessert or on lush green hill sides. But the one thing they all have in common is that nobody really knows why they were made.

How are Geoglyphs Made?

It really depends on the underlying landscape. In the case of the Nazca lines in Peru, the dessert surface is covered with a thin layer of pebbles coated in iron-oxide, below which the sands are light-coloured. All the people had to do was dig away the top 30 cm or so to create lines that can be observed from space and have been there as long as 1500 years. It is in fact easy to create visible disturbances in the dessert soil – as Greenpeace discovered in a ill advised stunt (like all their other stunts). What is remarkable with the Nazca lines is their size and the fact they are only visible (the ones that make pictures especially) from space. How exactly ancient people mapped out figures over the scale of miles that they couldn’t see remains a mystery.

For a long time chalk hill figures like the Uffington Horse in England were believed to be made simply by cutting away the top layer of turf to reveal the underlying chalk. However excavations have shown that trenches up to 1 metre deep were dug down into the chalk and that more chalk has been added from nearby quarries over the centuries to help maintain the patterns. The active maintenance is important as the turf could completely recover the image in as little as 20 years if left alone.

By contrast, a modern glyph the Marree Man in Australia, was recently restored with the use of a grader. This glyph was created by persons unknown in the 1990s, and it is believed that GPS technology was used to plot out the design. At that time the technology was in its relative infancy and the creators would have needed access to expensive equipment to achieve their results. There is even evidence that bamboo garden skewers were used to stake the shape out before ‘trenching’.

Archaeology of the Geoglyphs

But what do we actually know about these geoglyphs? Well, not very much because most glyphs do not have much associated archaeology. One of the big problems with trying to conduct archaeology on symbolic representations is that it’s impossible to know to what extent the stuff buried in the ground near the depiction is related to that depiction. Were the stone tools deposited by the cave painters, or did the presence of paintings draw later people (and their stone tools) to the cave?

For the famous Nazca Lines, they have been dated with the aid of pottery found near the lines, for example at intersection points. It is a landscape that is sparsely populated or utilised, so the relationships between the archaeology and the glyphs is considered reliable.
In recent years scientists have turned to new technologies for studying the lines, like aerial drones, photogrammetry, and AI, which has allowed them to discover many new glyphs, both in this region and other sites across South America.

Hill figures in England have even less associated archaeology. As noted earlier trenching has shown more work went into the creation of the images than was probably originally expected. One thing this archaeological work has provided was the opportunity to use novel techniques to accurately age the chalk figures. Optically Stimulated Luminescence (OSL) dating on the deepest layers of the Uffington Horse has shown it to be over 3000 years old, it vastly predates any other hill figure. Researchers at the horse have been making use of aerial photography, drones and also RAF photography, which covers at least 100 years in the region, to map out the shape and size of the horse to see if it has potentially shrunk or if its shape been changed. The answer is not by much.
Oxford Archaeology are currently involved in a study with the site and you can see their updates on their blog.

The Cerne Abbas Giant was dated with OSL and analysis of tiny snail fossils to a Late Saxon-Early Medieval age. This was a massive find as previously the most reliable dates (records referencing the figure) suggested it was from the late 1600s.

Why Were They Made?

The million dollar question, to which the answer is simply no one knows and there is probably no way of knowing absolutely. When it comes to symbolic behaviours in archaeology things can very rapidly descend into the realms to pure speculation and get very contentious. Generally, it comes down to weight of evidence and parsimony, that is the simplest explanation.

The Nazca lines are often associated with astronomical symbology, or as messages to the gods (since no one else can see them) but these are just one type of theory among many. Some of the straight lines appear to link communities so that they might act as navigational aides or processional ways for ceremonies unknown. Others are tenuously linked to water sources (above or below ground) and may be linked to either finding water or ceremonies linked to acquiring water. And of course there is a corner of the internet insisting they are the work of aliens.

For the Uffington Horse, the prevailing theory, that does not seem to have received any strong challengers, is that the horse is a depiction of a Sun Horse – drawing the sun across the sky – or something along those lines at least. Based on the once yearly event where the sun appears to rise right over the figure and on the prevalence of that particular symbology in ancient cultures.
What is interesting about the Horse is that despite nobody knowing what it’s for or even how long it has been there, local communities have remained invested in it. There are records dating back centuries of regular re-chalking events (ED: scourings (added 19/09/2024)), which often became large community events. Re-chalking continues to this day.

By contrast the Giant has had a very chequered past. It has been suggested to be a depiction of an Anglo-Saxon deity (Heil / Helith) or a Roman depiction of Hercules or a saint associated with the nearby Abbey. Quite frankly no body knows. And the interpretations have been further confused as the drawing itself has changed over time. With some researchers claiming there is evidence for Anglo-Saxon style additions (like a cloak) that are now lost. But this may be misleading as there is something of a tradition of altering the Giant. In 2020 unknown persons added a face mask to the depiction (something the local community, suffering under lock downs, reportedly enjoyed). And in the past the giant has had his prominent member dedicated to some one’s beloved. There are no records of what the recipient thought of the unusual love letter. On another occasion a football was supplied for his entertainment. None of these alterations lasted because chalk figures must be regularly maintained, and they have been publicly frowned upon by the National Trust.

What is the Value of a Geoglyoph?

Geoglyphs are fascinating, but it is the reactions and interactions of modern communities to these depictions that interests me the most. Centuries of communities coming together to re-chalk a depiction that no one can explain the meaning or origin of. Or communities altering the chalk figure to reflect the attitudes and priorities of the modern people living nearby. A remote Australian community raising funds and conducting research to rehabilitate a geoglyph that was built in their own lifetimes. And even, in the case of the Nazca lines, the communities’ and the Peruvian government’s offence when the lines were damaged by the reckless behaviour of outsiders. And yes, there are tourist dollars attached to all these sites but there is also a profound sense of pride and community. Archaeologists may look at these depictions as paintings frozen in time, but to their communities they are a living and possibly evolving part of their personal heritage. We can debate, people seem to massively enjoy doing so, their origins and meanings, but ultimately their value is not in what they meant to ancient peoples but in the value and identity they provide to modern communities.