The urgency of the work is grounded in real events. At Xocén, the roof of an underground cavern gave way suddenly in the middle of a Maya community, toppling a two-century-old Ceiba tree and opening a sinkhole roughly 57 meters in diameter and up to 36 meters deep. The researchers believe intense rainfall and the passage of heavy construction machinery in the days before the collapse triggered the failure of a cavern ceiling that had been weakening for a long time below the surface. At Saamal, an open cenote popular with visitors, partial collapse of the steep cliff walls suggests that even mature, apparently stable karst features can remain structurally active for years.

The scientific setting is extraordinary. The Yucatán’s cenote density traces back to the Chicxulub impact crater, the roughly 200-kilometer-wide scar left by the asteroid that ended the Cretaceous period. The crater’s fractured rim created a zone of enhanced permeability, the so-called Ring of Cenotes, along which carbonate dissolution concentrated over millions of years. When acidified rainwater percolates through limestone, it enlarges fractures and voids until the remaining roof can no longer support its own weight. Because karst terrains show few visible warning signs at the surface until failure occurs, they account for a disproportionate share of sudden ground-collapse hazards worldwide.

Conventional geotechnical investigation relies on drilling and excavation, methods that are expensive, slow, and impractical to deploy across many sites immediately after a collapse. ERT offers an alternative. By injecting electrical current into the ground through arrays of electrodes and measuring the resulting voltage differences, the technique produces cross-sectional images of subsurface resistivity. Competent dry limestone appears highly resistive, while water-saturated, clay-rich, or heavily weathered rock conducts electricity well. Air-filled voids also register as strong resistive anomalies. These contrasts map directly onto the mechanical properties that govern collapse susceptibility.

At Xocén, the team deployed a Syscal Pro system with Wenner and Schlumberger electrode arrays along three profiles totaling up to 110 meters each, reaching effective investigation depths of roughly 16 to 25 meters. After filtering unreliable readings and inverting the data with a smoothness-constrained least-squares algorithm, the final models achieved root-mean-square misfits between about 2 and 2.5 percent. The inverted sections revealed a consistent vertical stratification: a resistive cap of dry limestone more than 1000 ohm-meters, an intermediate transition zone of partially weathered rock, and a laterally continuous conductive interval below 250 ohm-meters interpreted as water-saturated, highly altered limestone, whose top approximates the local water table.

Most striking was a vertically persistent conductive anomaly in one profile, where resistivity dropped below 150 ohm-meters, linking the surface to the deep conductive layer. The researchers interpret this feature as a fracture-controlled infiltration corridor, a preferential pathway through which water percolates, accelerating dissolution and progressively weakening the rock mass. This geometry suggests that the Xocén collapse was not an isolated surface event but the geomorphological expression of a pre-existing weakened subsurface domain, with future instability most likely concentrated at the interfaces between the resistive cap, the transition zone, and the deeper conductive material.

At Saamal, five closely spaced profiles were acquired along the vulnerable cliff rim using a SuperSting R8 system, with electrodes just one meter apart to resolve the approximately 3-meter-thick limestone ledge involved in the recent failures. A robust, blocky inversion captured the sharp contrasts near the wall. The sections showed a thin weathered conductive veneer half a meter to a meter thick overlying competent carbonate rock, plus a very high-resistivity domain exceeding 1600 ohm-meters adjacent to the cliff, interpreted conservatively as a dry, possibly fractured carbonate block. Because air-filled cavities and dry rock yield similarly high resistivities, the authors caution that resistivity magnitude alone cannot confirm open voids. To visualize domain continuity between profiles, the team trained a neural network to interpolate the independently inverted two-dimensional sections into a three-dimensional resistivity volume, a supporting tool rather than a true 3D inversion.

A depth-of-investigation analysis following the established Oldenburg and Li method confirmed that the models are constrained by real data to mean depths of about 19.7 meters at Xocén and 2.9 meters at Saamal, guarding against over-interpretation of poorly resolved regions. The authors are candid about limitations: no borehole, geotechnical, or piezometric control was available, so the inferred domains remain hydrogeophysical rather than directly verified, and the resistivity thresholds are site-specific rather than universal. They recommend corroboration through fracture mapping, ground-penetrating radar, shallow seismic surveys, and repeat ERT monitoring after rainfall events.

The broader significance lies in translating geophysical images into operational disaster-risk decisions. The study proposes that collapse-prone sectors be identified not by a single universal signature but by site-specific combinations of shallow weathered conductive veneers, laterally connected saturated zones, fracture-controlled infiltration pathways, and sharp resistivity interfaces. Classifying ground into high, intermediate, and low susceptibility zones gives authorities a defensible basis for restricting access, prioritizing monitoring, and planning land use around cenotes in populated or heavily visited areas. As reported collapses of cenote roofs increase across the Yucatán, this rapid, affordable screening framework offers communities and tourism operators a practical first line of defense against one of nature’s most sudden geological traps.

Subject of Research: Electrical resistivity tomography screening of collapse susceptibility in karst cenote environments of the Yucatán Peninsula, Mexico

Article Title: Electrical Resistivity Tomography for collapse susceptibility screening in karst cenote environments: A case study in the Yucatán Peninsula, Mexico

Article References: Juárez, S. L., Coyoacán, Aleman, J. C. O., Castañeda, C. C., Hernandez, J. F. E., Perez, D. A. P., & Martinez, J. M. (2026). Electrical Resistivity Tomography for collapse susceptibility screening in karst cenote environments: A case study in the Yucatán Peninsula, Mexico. Environmental Challenges, Article 101642. https://doi.org/10.1016/j.envc.2026.101642

Image Credits: AI Generated

DOI: Not provided

Keywords: cenotes, karst, electrical resistivity tomography, Yucatán Peninsula, sinkhole collapse, Chicxulub crater, geophysics, Xocén, Saamal, disaster risk, limestone dissolution, Ring of Cenotes