Powerful phreatic eruption at Santa Teresa ausol blocks road in Ahuachapán, El Salvador

A powerful phreatic eruption occurred at the Santa Teresa ausol, part of the Los Ausoles geothermal field in Ahuachapán, El Salvador on July 10, 2025. The eruption ejected a column of boiling water, steam, and sediment, blocking an access road and damaging surrounding infrastructure. No injuries were reported.

A powerful phreatic eruption occurred at the Santa Teresa ausol in Cantón El Barro, Ahuachapán Department, El Salvador at 16:55 LT on July 10. The event was captured on CCTV footage, showing a sudden vertical and lateral ejection of steam, water, and sediment from the thermal vent.

The Santa Teresa ausol, located within the Los Ausoles geothermal area, is the largest thermal feature of its kind in Central America. It has a diameter of approximately 70 m (230 feet) and a depth of 20 m (66 feet), with recorded vent temperatures from 300°C–350°C (572°F–662°F). The Los Ausoles geothermal field covers roughly 20 km² (7.7 mi²) and contains over 130 active geothermal features including mud pots, fumaroles, and steam vents.

Yesterday’s explosion deposited volcanic mud and debris onto a road that connects to a popular hot spring facility, prompting authorities to temporarily close access. Civil Protection units and firefighters responded, assessed hazards, and established a 75 m (246 feet) exclusion zone around the site. Seventeen residents were evacuated as a precaution.

There were no immediate reports of injuries. However, minor structural damage to tourist facilities and access routes was reported by municipal sources.

The Santa Teresa ausol previously erupted in 1989, resulting in at least 32 fatalities. It remains the most active and hazardous feature within the Los Ausoles geothermal field, which also serves as a site for rural tourism and geothermal energy exploration.

Phreatic eruptions, also known as hydrothermal explosions, occur when water trapped in underground reservoirs is rapidly converted to steam by contact with hot rock.

Such explosions are typically non-magmatic, triggered by the interaction of groundwater with high-temperature rock. The US Geological Survey (USGS) and similar agencies warn that these systems are highly unpredictable due to complex subsurface conditions and limited instrumentation coverage.

Featured image credit: CCTV

Reet Kaur

I’m a science journalist and researcher at The Watchers, contributing to the Epicenter edition, where I cover peer-reviewed scientific research and emerging discoveries across Earth and space sciences. With a background in astronomy and a passion for environmental science, I’ve worked in shark and coral conservation in Fiji, conducting reef and shark-behavior research, contributing to mangrove restoration, and earning PADI Open Water and Coral Reef Certifications. I bring a blend of scientific rigor and storytelling to illuminate the discoveries shaping our planet and beyond.

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