Chichón Volcano Shows Fresh Signs of Hydrothermal Activity

Unusual physical and chemical changes inside the crater of Mexico’s Chichón volcano have drawn renewed scientific attention, raising concerns about a dynamic hydrothermal system beneath its crater lake. While no imminent eruption is expected, researchers say the volcano is no longer geochemically stable and requires closer monitoring.

Rising Temperatures and Gas Emissions

Scientists monitoring the crater lake detected a series of anomalies between June and December 2025. Surface temperatures in the lake repeatedly reached up to 118°C, well above typical geothermal levels. Field teams also observed visible gas bubbling, with increased emissions of hydrogen sulfide and carbon dioxide. These gases, though common in volcanic systems, can accumulate to dangerous levels in confined crater environments.

Sulfur Spheres and Chemical Shifts

Researchers from the National Autonomous University of Mexico reported the appearance of floating hollow sulfur spheres, formed when volcanic gases rise through pools of molten sulfur beneath the lakebed. The lake’s colour has shifted from algae-dominated green to a greyish hue, reflecting higher concentrations of sulfates and silica. Significant fluctuations in chloride levels further indicate changes in subsurface fluid circulation.

Legacy of the 1982 Eruption

Chichón’s current activity is viewed through the lens of its devastating 1982 eruption, one of the deadliest in modern Mexican history. That event killed over 2,000 people, buried entire settlements, and injected massive amounts of sulphur dioxide into the stratosphere, briefly cooling global temperatures. The eruption reshaped the summit, forming the crater lake that now serves as a sensitive indicator of internal processes.

Important Facts for Exams

• El Chichón volcano is located in Chiapas, southern Mexico.
• The 1982 eruption caused major loss of life and global climatic effects.
• Hydrothermal activity involves heated water and gases, not magma movement.
• Phreatic eruptions are steam-driven and can occur without warning.

Monitoring Gaps and Future Risks

The volcano remains under a yellow alert, phase two, indicating abnormal but non-eruptive activity. However, gaps in real-time seismic, gas, and thermal monitoring limit precise risk forecasting. Institutions such as CENAPRED are now deploying drones and remote sensing tools to strengthen surveillance. Scientists warn that while magma ascent is unlikely, steam-driven explosions remain possible, underscoring the need for sustained observation and community preparedness.