Poás Volcano remains under orange alert due to increased seismic activity and ash emissions. Recent eruptions have propelled ash columns up to 4 kilometers high, leading to temporary closures of the national park and heightened monitoring by authorities.

Poás Volcano: A Persistent Force in Costa Rica’s Landscape

Rising to 2,697 meters (8,848 feet) in the heart of Costa Rica, Poás Volcano is one of the country's most iconic—and most active—stratovolcanoes. Located within the boundaries of Poás Volcano National Park, this geological giant has erupted more than 40 times since records began in 1828.

A Volatile History

One of the most disruptive recent eruptions occurred in April 2017, forcing the evacuation of both tourists and local residents. In the wake of explosive activity, the park was shuttered for nearly 17 months, with a 2.5-kilometer exclusion zone established around the crater. It partially reopened to the public on September 1, 2018, with controlled access to the crater viewpoint. Visitors were required to book in advance via the National Park’s website. However, many trails, including those leading to Lake Botos and the on-site museum, remained closed. That same year, brief eruptions occurred twice in September.

The Crater Lakes

Poás is home to two distinct crater lakes near its summit. The northern lake, *Laguna Caliente*, is one of the most acidic bodies of water on the planet. Located at around 2,300 meters elevation and approximately 300 meters wide, the lake’s pH can drop close to zero following rainfall or heightened volcanic activity. A layer of molten sulfur lines the lakebed, and only extremophile bacteria like *Acidiphilium* can survive its hostile waters. The lake’s emissions of sulfur and acidic vapors often damage surrounding ecosystems and pose health risks to visitors and wildlife.

In contrast, *Lake Botos*, situated in an inactive crater, is a cold, pristine lake ringed by lush cloud forest. Its last eruption occurred around 7500 BC. As of April 2023, the trail to Lake Botos has reopened, offering a glimpse of the park’s quieter side.

Notable Eruptions and Seismic Events

A significant eruption cycle began in 1953 and lasted until 1956, during which two people were reported missing. More recently, a magnitude 6.1 earthquake in January 2009 caused widespread damage and loss of life across the Central Valley. That same year, Poás experienced minor phreatic eruptions and landslides within its active northern crater.

In 2014, a dramatic ash explosion was captured on camera by Costa Rica’s Volcanological and Seismological Observatory (OVSICORI), showcasing the volcano’s continuing activity. Poás is one of nine volcanoes included in the Deep Earth Carbon Degassing Project, which monitors carbon dioxide and sulfur dioxide emissions worldwide.

2017 Eruptions and Park Closure

In early April 2017, rising levels of toxic gases prompted park officials to restrict visitor access. A powerful eruption on April 12 forced a full closure, followed by a series of explosive events over the following days. On April 22, an eruption hurled incandescent rocks and damaged infrastructure. President Luis Guillermo Solís visited affected towns and released a bilingual message encouraging tourists to support nearby businesses despite the park’s closure.

By September 2018, the park reopened with a new reservation system, restricted time at the crater, and limits on the number of daily visitors.

Poás remained restless in 2019. On February 11, an early-morning eruption sent ash 200 meters into the air. A more powerful event followed on September 30, launching ash and volcanic material 2 kilometers high—surpassing the milder steam-driven emissions seen just days earlier.

2025: A Year of Uncertainty

Volcanic activity surged again in 2025. In early March, small eruptions escalated into more significant events. A 400-meter plume was recorded, and the park’s alert level was raised to Level 3. Temporary closures followed, and new safety protocols were introduced—limiting visitor groups to 56 people, shortening stay durations, closing trails, and mandating helmets for crater visitors.

By mid-March, seismic activity intensified with more than 200 quakes recorded in just 24 hours on March 18. On that same day, sulfur dioxide emissions soared to 691 tons—double the earlier monthly figures. The hyperacidic crater lake began shrinking rapidly.

On March 28, two ash columns each reached 200 meters high, with volcanic projectiles hurled over 150 meters. The Ministry of Environment and Energy (MINAE) and SINAC responded by indefinitely closing the park on recommendations from the National Emergency Commission (CNE).

The volcano’s peak activity came on April 21, when it released a 4-kilometer-high ash plume—the tallest since 2017. Ashfall affected communities as far as Sarchí and Grecia, and the eruption was visible from San José and Alajuela. In the days that followed, Poás expelled hundreds of rocks with surface temperatures approaching 300°C.

Today, Poás remains under close observation, a stark reminder of Costa Rica's dynamic and ever-changing volcanic landscape.