Around 4,900 years ago, Neolithic communities on the Danish island of Bornholm ritually buried hundreds of engraved stones, so-called “sun stones,” in a remarkable act to counter drastic climate changes caused by a mᴀssive volcanic eruption. The eruption was identified in ice cores by the Niels Bohr Insтιтute at the University of Copenhagen as having caused a period of cold and darkness and severely affecting early agricultural societies.

Plaques with solar motifs discovered in Vasagård, Denmark. Credit: John Lee, The National Museum of Denmark

The volcanic event, which occurred around 2900 BCE, spewed large amounts of sulfur into the atmosphere, forming a haze that blocked sunlight. This, in turn, caused temperatures to fall and significantly reduced sunlight—a challenge that led to crop failure and proved to be an existential threat, particularly to Neolithic farmers. Researchers compared its effects to a later eruption in 43 BCE, which caused agricultural collapse and famine across the Mediterranean.

More than 600 sun stones have been unearthed during archaeological excavations at Vasagård on Bornholm. These flat stones were made of shale, often carrying patterns and motifs related to the sun—symbolically ᴀssociated with fertility and cosmic equilibrium. Animal bones and pieces of broken earthenware accompanied these stones, along with flint tools, in ceremonial ditches. Dr. Rune Iversen from the University of Copenhagen suggests that the sacrifices were likely intended to restore sunlight and ensure agricultural prosperity.

Scientific evidence closely aligns with the timing of these sacrifices. Ice cores from both Greenland and Antarctica show a significant sulfur signature around 2900 BCE, indicating the volcanic eruption. Other evidence comes from the sediment layers of lakes in Germany and dendrochronological studies from the U.S., which confirm a period of low sunlight and an extremely unfavorable climate.

Plaques with field and plant motifs. Credit: René Laursen, Bornholms Museum

This era was marked by widespread upheaval in Northern Europe. DNA analyses of human remains also showed that plague infections contributed to the environmental catastrophes. The Funnel Beaker culture was already in decline during this period and was replaced by new traditions. The ritual ditches for sun stone sacrifices in Vasagård were gradually replaced by a wooden palisade and circular cult houses, reflecting changes in social and religious life.

The ritual significance of sun stones mirrors other ancient solar veneration practices, such as the construction of Stonehenge in England. Vasagård’s alignment with solstices underscores its role as a center of sun worship. Visitors to the National Museum of Denmark can view several of these enigmatic artifacts, which represent some of the earliest evidence of solar-focused rituals in Scandinavia.

More information: Iversen R, Nielsen PO, Sørensen LV, et al. (2025). Sun stones and the darkened sun: Neolithic miniature art from the island of Bornholm, Denmark. Antiquity. 1-17. doi:10.15184/aqy.2024.217