Volcanos

Roundup of Global Volcanic Activity

Shishaldin (Aleutian Islands, Alaska): The alert level was lowered back to normal status. Detectable activity (visible observations and satellite-based data) has been decreasing steadily of the past several months, the Alaska Volcano Observatory reported: "There has been a steady decrease in detected thermal activity at Shishaldin over the past several months. No anomalous activity has been observed in several clear satellite images of Shishaldin since moderately elevated surface temperatures were detected on Jan. 13. Airwaves associated with low-level explosive degassing have not been detected in infrasound data since Feb. 7. Low-amplitude seismic tremor consistent with an open, degassing system continues to be seen in seismic data and is considered to be within the bounds of background activity for Shishaldin. AVO is therefore downgrading the status of Shishaldin Volcano from aviation colour code YELLOW to GREEN and from volcano alert level ADVISORY to NORMAL."

Rincón de la Vieja (Costa Rica): The volcano had a new explosion from its crater lake last Wednesday 8 March. The eruption threw deposits of mud and ash onto the northern side of the crater to up to 120 m distance from the rim and generated a small plume of ash that caused light ash fall in nearby villages in up to 6 km distance to the north. The activity at the volcano had started to increase already in 2015. Volcanologists have found evidence of several similar explosions that occurred in the past months, but the most recent one on Wednesday seems to have been significantly larger (although still small in itself). The most interesting news, however, comes from the analysis of the ejected ash. OVSICORI-UNA staff found that besides fragmented older rocks and sulphur, about 3-10 % of the ejected ash particles are glassy shards from juvenile (i.e. new) magma.