OVSICORI-UNA reported that phreatic explosions continued at Rincón de la Vieja during 6-13 June, with multiple phreatic events recorded during 6-8 June. A 14-minute-long event that began at 0142 on 7 June was comprised of two pulses of gas-and-steam that rose 1 km above the crater rim. At 0942 on 8 June a plume of steam and gas rose 2.5 km above the crater rim, followed at 1810 by a moderate phreatic eruption that ejected lake water with sediment to less than 100 m above the crater rim and produced a white steam plume that rose 3 km and drifted W. Two events recorded at 0138 and 2037 on 9 June were similar in energy to the 8 June event at 1810. Gas emissions were visible on 10 June. Small phreatic events at 0357, 0521, and 0546 on 11 June produced white steam-and-gas plumes that drifted W. White steam-and-gas plumes from small phreatic events at 1031 and 1039 on 12 June rose as high as 1 km above the crater rim.

Geological Summary. Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge 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. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide 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 historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.

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