Attachments
Description of the Event
Approximate date of impact
A dormant or active volcano generated eruptions and landslides unpredictably, often without early precursory signals detectable in advance in real time.
The inherent unpredictability of volcanic activity meant that precise predictions of the date of impact remained elusive. Instead, efforts focused on providing early warnings, closely monitoring volcanic activity, and implementing effective risk management strategies to minimize the impacts of eruptions on human lives and property.
Provide any updates in the situation since the field report and explain what is expected to happen.
Volcanologists from the Costa Rican Volcanological and Seismological Observatory (OVSICORI) indicated that the current activity pattern of the Poás Volcano was similar to that observed in 2019, when the drying of the volcano’s lagoon caused rock fracturing and subsequent ash emissions. Although the volcano’s behavior did not change significantly, ash emissions continued.
On 1 April 2024, the National Emergency Commission (CNE) declared a Green Alert for Poás Volcano, affecting Poás, Grecia, Naranjo, Sarchí, Zarcero, and the central canton of Alajuela due to continuous ashfall and gas emissions since 29 March. An estimated 518,948 residents in these cantons were at risk (1).
On 3 April, representatives from various institutions, including the CNE and the Ministry of Environment and Energy (MINAE), met to discuss the situation. The CNE noted that wind and low atmospheric humidity also contributed to the dispersal of materials expelled by the active volcano directly into the atmosphere, reaching more distant areas and affecting nearby communities (2).
The Ministers of Environment and Energy, and of Agriculture and Livestock, reiterated the safety protocols in the park and preventive measures to protect the population and farmers in the area. The president of the CNE emphasized the importance of continuous monitoring of the volcano and inter-institutional coordination to ensure the safety of residents and visitors in the affected areas.
On 4 April, OVSICORI reported incandescence in the volcano's crater and an ash column that rose at least 300 meters high (3).
Between 24 and 30 April, according to the latest weekly report by the Smithsonian Institution and the US Geological Survey, OVSICORIUNA reported continued gas-and-steam emissions from vents Boca A and Boca C on the crater floor of Poás. Although emissions from Boca C occasionally contained low ash content, no ash was detected between 25 and 27 April. Plumes intensified on 28 April, rising several hundred meters high. A sulfur odor was reported in Sarchí and Grecia (both about 17 km SW) on 25 April. Incandescence from Boca A was visible at night on 27 and 28 April, and from both Boca A and Boca C at night on 29 and 30 April (4).
According to the latest Situation Update issued on 26 April by OVSICORI, although there seemed to be a decreasing trend in seismic activity and degassing, which was also reflected in eruptive activity, it was important to consider that the conduit remained open, and there was a possibility of a sudden increase in volcanic activity due to potential variations in the volcanic system. Such changes could lead to unpredictable phreatic eruptions, projecting acidic and ballistic sediments toward El Mirador for visitors and other surrounding areas. Furthermore, with the onset of the rainy season, acid rain was a potential risk (5).
Authorities continued to monitor the situation. At the same time, the Costa Rican Red Cross began collaborating with authorities to ensure safe access during monitoring visits.