Micro-pingos on a bridge in Amsterdam

Abstract

In early 1979, an unusual geomorphological phenomenon was observed on a drawbridge in Amsterdam, Netherlands. A series of dome-shaped upheavals appeared displaying characteristics similar to miniature pingos. These features varied in size and exhibited progressive deformation, including surface cracking and summit collapse. The bridge's layered structure (steel, wood, and asphalt) created unique thermal and hydrological conditions. It is hypothesised that water infiltrated the steel–wood interface, forming ice lenses during freeze events. The inverse temperature gradient, driven by sub-bridge cooling, facilitated upward ice growth. Additional expansion due to differential swelling of wooden blocks contributed to further deformation.