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A pit filled with heat stones from the rescue excavation in Heimberg. Source: Archaeological Service of the Canton of Bern / Guy Jaquenod

Bronze Age Pits in Switzerland Reveal Secrets of Clay Production

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Ahead of a new road building project in Switzerland, archaeologists excavated what they assumed was a Roman settlement. However, it was only when they discovered a series of pits filled with hearth stones, which amplified and retained heat, that they realized they were digging into a pre-Roman Bronze Age site.

Exploring Bronze Age Pits and Posts: Lost Legacies Revealed

Last Autumn, in Heimberg, Switzerland, the Archaeological Service of the Canton of Bern were excavating what they believed was a Roman archaeological site, ahead of a road construction project. However, the team were taken-aback when they began unearthing Bronze Age artifacts.

During the Bronze Age great advances were made in the mastery of bronze metallurgy, which revolutionized tool and weapon production. Leaps ahead were also made in the processes of extracting and manipulating clay. This resulted in the emergence of complex societies and the establishment of the first cities with centralized political structures and social hierarchies.

The excavation site spans around 1,000 square meters [10763.9 sq ft] and the archaeologists reported discovering “a high proportion of hearth stones and a significant quantity of Bronze Age pottery, alongside post positions and pits,” announced the Canton of Bern.

Two of the Bronze Age pits were completely filled with hundreds of selected hearth stones, and the researchers suspect they served as “heat accumulators,” a characteristic feature during the Bronze Age. It was through melting oars for tools and weapons, as well as extracting clay for manufacturing pottery, that people in the Bronze Age learned that deep beds of prepared charcoal and rocks provided superior heat to that generated by simple campfires.

The excavation in Heimberg, on the right edge of the area there is a pit filled with heat stones. (Archaeological Service of the Canton of Bern / Daniel Breu)

The excavation in Heimberg, on the right edge of the area there is a pit filled with heat stones. (Archaeological Service of the Canton of Bern / Daniel Breu)

Charting the Heritage of Clay Manufacturing at Bronze Age Pits

The scientists identified layers of clay up to 35 meters (114.829 ft) deep, which they say highlights the significance of clay at the site. They suggest clay “played a vital role in the settlement” within house construction, for example, when “plastering wattle walls and crafting pottery vessels.” Therefore, the Bronze Age pits filled with rocks most-probably functioned in the achievement of heat within the clay extraction process.

While advancements in alloys were made during the Bronze Age, clay never lost its value. This is evident in that the researchers found the clay deposit was later used by a brick factory in Heimberg, in 1964. Therefore, the researchers are speculating on a continuity of clay extraction and ceramic production in this region “since Roman times.”

Bronze Age ceramics recovered as a block from the rescue excavation in Heimberg. (Archaeological Service of the Canton of Bern / Frédérique Tissier)

Bronze Age ceramics recovered as a block from the rescue excavation in Heimberg. (Archaeological Service of the Canton of Bern / Frédérique Tissier)

Bronze Age Pits Help Mold the History of Swiss Clay

The extraction of clay for the manufacture of pottery is first recorded in Europe in the early Neolithic period, starting in England around 4000 BC according to Historic England. However, at this time the artisans were using very limited technologies. Last year, aiming to learn more about the methods of clay extraction and processing during the Roman period in Switzerland, another team of researchers analyzed “893 Roman crucibles,” according to a 2023 study.

The results of these tests identified five individual clay groups, with some of them being situated 31 miles (50 km) away from where the clay was found. This finding suggested the existence of clay transport and distribution networks across Roman Switzerland, which may have utilized earlier Bronze Age trade routes.

Now, the discovery of rock-filled Bronze Age pits for heating clay in Heimberg greatly adds to the advancing research into clay production in Bronze Age and Roman Switzerland. In conclusion, the researchers said their work adds to the emerging map of transportation routes connecting the Alps with the Swiss plateau, and greater Europe.

Top image: A pit filled with heat stones from the rescue excavation in Heimberg. Source: Archaeological Service of the Canton of Bern / Guy Jaquenod

By Ashley Cowie

 
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Ashley

Ashley is a Scottish historian, author, and documentary filmmaker presenting original perspectives on historical problems in accessible and exciting ways.

He was raised in Wick, a small fishing village in the county of Caithness on the north east coast of... Read More

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