Rock carving depth reflects carvers’ geological insight

Bronze Age rock carvers in Tanum demonstrated remarkable geological insight by selecting and engraving panels with pre-existing microfracture zones, allowing deeper carvings than previously thought possible. The study reveals that carvings, averaging 0.96–1.52 mm deep, were confined to the first weak layer of Bohus granite, exceeding post-glacial weathering limits (≤1 mm). Using ultrasonic B-scans and photogrammetry, researchers identified reflective horizons at ~8-20 mm depth, consistent with paraglacial stress-relief microfractures. This suggests carvers strategically chose locations based on geological conditions, challenging the assumption that weathering was the sole limiting factor for carving depth.

Liebl, C., Peternell, M., Horn, C., Ling, J., Moyano Di Carlo, J., Green, A., & Potter, R. (2026). Rock carving depth reflects carvers’ geological insight. PLOS One, 21(9), e0358075. https://doi.org/10.1371/journal.pone.0358075