OVSICORI-UNA reported that the level of the water lake in Rincón de la Vieja’s summit crater declined during 30 May-21 June based on drone footage. A small phreatic eruption occurred at 0607 on 22 June. Several small phreatic eruptions were recorded overnight during 25-26 June. A small event at 0547 on 26 June produced a steam-and-gas plume that rose 1.5 km above the crater rim. Another small event at 0308 on 27 June produced a gas-and-steam plume that rose more than 1 km, though weather clouds and darkness obscured views. The Alert Level remained at 3 (the second highest level on a 0-4 scale).

Geological Summary. Rincón de la Vieja is a volcanic complex in the Guanacaste Range of NW Costa Rica. Sometimes referred to as the Rincon de la Vieja-Santa María Volcanic Complex, it consists of a slightly arcuate 20-km-long ridge of 12 craters and pyroclastic cones constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the "Colossus of Guanacaste," it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. The Santa María cone, the highest peak of the complex, is located on the E side of the ridge and has a lake within the 400-m-diameter crater. A Plinian eruption producing the 0.25 km3 Río Blanca tephra about 3,500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous reported eruptions possibly dating back to the 16th century, have been from the active crater, near the center of the complex, with an acidic 300-m-diameter lake.

Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)