Who created the largest snake mound in the world?

In the eastern United States, nestled among the trees beside a tributary of the Ohio River, lies one of the strangest and most mysterious man-made structures ever created. The Great Serpent Mound is just under a meter high, but stretches over 400 meters and is clearly visible from above.

This particular mound is built mainly from a layer of yellow clay.

The Great Serpent Mound is considered the largest snake mound in the world. The first written records of the site come from surveys conducted in the 19th century by Ephraim Squier and Edwin Davis. They wrote about the mysterious mound in their 1848 history book , Ancient Monuments of the Mississippi Valley .

In fact, the entire structure of the snake mound is divided into three sections, with the snake shape stretching 419 meters long and 6 to 7.6 meters wide. The head of the snake approaches a cliff above a stream, with the rear body winding back and forth.

The distinctive mound itself is built primarily from a layer of yellow clay and was reinforced with a layer of stone before being covered with earth. The head of the snake appears to be trying to devour a circular mound of earth about 37 meters long.

There has been some debate among scholars as to whether the distinctive shape of this mound represents an egg or the Sun or some other specific object.

The entire structure of the snake mound is divided into three parts with an elongated snake shape.

Interestingly, similar snake mounds have been found elsewhere in the world , including Scotland and Canada. And, given their vertical shape, with a low height relative to their other dimensions, this snake mound falls into the same category as Peru's Nazca Lines. These structures are suitable for aerial observation – something that would have been impossible in the era in which they were created.

Archaeologists have debated the origins of the snake mound for decades. Many excavations have been carried out, but no artifacts or burials have been found that can directly help determine when it was formed or why it was built.

 No artifacts or burials were found around the snake mound area.

There are currently two leading theories as to who may have built this giant snake-shaped structure. Some believe it may have belonged to the Adena culture , which dates from 800 BC to around 100 AD.

Others believe it was built by the Fort Ancient culture that existed between 1000 and 1750 AD. This theory also suggests that the giant snake mound was built around the 11th century.

With the two hypotheses above, the age of the snake mound is also inconsistent - millennia apart. So why is there this uncertainty, and why are there such wildly different hypotheses?

The Adena culture is an ancient culture known to have flourished on the North American continent. William Webb, a renowned researcher, found evidence of this culture in Kentucky as early as 1200 BC.

Comparing the artifacts found in Kentucky with those found near the Snake Mound, the team believes it was built by the same culture, and the Adena culture is known to have spread as far as the Ohio Valley. The Adena culture is also known to have built large mounds elsewhere, although they do not resemble the Snake Mound in shape.

An eight-member team led by archaeologist William Romain investigated charcoal samples from the snake mound. The findings dated the construction to between 381 BC and 44 BC, which fits well with the peak of the Adena culture at the site.

Contrary to this theory, the snake mound belongs to the Fort Ancient culture. In 1996, a team led by Robert Fletcher and Terry Cameron reopened some of the 19th century excavations.

They found charcoal in the excavations, and when tested, the samples were dated to around 1070 AD. This therefore seems to suggest that the Fort Ancient culture, who inhabited the Ohio Valley at the time, built the snake mound, and that it was probably built on top of earlier smaller mounds built by the Adena culture.

But there are problems with this theory itself. Mound building was not typical of the Fort Ancient peoples. The mound also contained no distinctive artifacts, and no notable burials were found near the snake mound, which is unusual for the Fort Ancient culture.

However, many believe that both theories could be true. Perhaps the Adena culture created the original mound, and then a thousand years later, the Fort Ancient culture repaired the parts of the mound that had been damaged by time.

The mound may have been used to determine time or the changing of the seasons.

Based on research conducted in 1987, it is believed that the circular mound and the head of the snake align with the setting sun on the summer solstice. Meanwhile, the tail of the snake points toward the rising sun on the winter solstice.

This suggests that it may have been used to determine the timing or change of seasons . This method may have given advice to local people on when to sow or harvest crops.

Additionally, the curves on the snake's body have been determined to parallel the phases of the Moon, alternating with the two solstices and two equinoxes.