Volcán Poás (Poás volcano), one of the most active in Costa Rica, looms over the country’s capital and largest city, San José.
Volcán Poás (Poás volcano), one of the most active in Costa Rica, looms over the country’s capital and largest city, San José. During quiet periods, people ascend its slopes and peer into its summit crater, where a hot, sulfurous, and acidic lake seethes. The restless stratovolcano has erupted dozens of times in the past 200 years, propelling plumes of ash and volcanic gases that sometimes carry into nearby communities.
Poás was rumbling to life again in early March 2025, when the OLI (Operational Land Imager) on Landsat 8 acquired the images above and below. The Volcanological and Seismological Observatory of Costa Rica (OVSICORI-UNA) reported frequent steam-driven, or phreatic, eruptions in its crater from March 4 to March 7. Other data suggested an increased probability of impending dangerous eruptions, prompting authorities to issue the third-highest volcanic alert level (out of four).
Periodic eruptions continued at Poás from early March through at least mid May, though persistent cloudiness prevented Landsat sensors from capturing a clear image of the activity. OVSICORI-UNA observed plumes of steam, volcanic gases, and sometimes ash shooting more than a kilometer into the air throughout this eruptive period. High levels of sulfur dioxide degraded air quality in cities and towns nearby, and ashfall damaged some coffee crops and pastures, according to news reports. The observatory also noted a red glow in the crater in early May, which they attributed to the combustion of sulfur deposits.
Read More: NASA Earth Observatory
Photo Credit: NASA Earth Observatory
