1,000-year-old Ihuatzio Pyramid damage linked to cracking, water infiltration and climate intensity

The partial collapse of the pre-Columbian pyramid at the Ihuatzio Archaeological Zone in Michoacáno on July 29 last year, has underscored the vulnerability of ancient masonry structures to intensifying climate pressures. The affected pyramid, approximately 15 meters tall, was one of two major stepped monuments within a complex first occupied more than 1,100 years ago. Long-term settlement, previous restoration works using outdated materials and techniques, and structural discontinuities created conditions that allowed water infiltration to progress over time.

According to assessments by Mexico’s National Institute of Anthropology and History (INAH), the region experienced severe drought prior to the July rainfall event. Prolonged desiccation created micro-cracks in the stone and fill materials, reducing internal cohesion. When intense rainfall arrived, water rapidly infiltrated these weakened pathways. The sudden moisture load increased pore pressures within the masonry core, decreased shear resistance, and led to a localised internal landslide along the south wall. At least six stepped bodies were damaged, affecting both exterior blocks and the structural core.

The event is part of a wider trend affecting heritage sites across Mexico and beyond. Severe weather, including alternating drought and intense rainfall, has accelerated deterioration in archaeological structures in Europe, Oceania, and Southeast Asia. The collapse at Ihuatzio follows similar concerns in Utah and other global sites where rapid shifts in moisture regimes have caused stone instability. INAH has filed insurance claims and initiated restoration measures to stabilise the remaining structure. The case highlights the need for climate-responsive conservation strategies, including monitoring of moisture cycles, improved drainage, and reinforcement methods tailored to ancient masonry systems.