Volcanos

Roundup of Global Volcanic Activity

Cleveland (Aleutian Islands, Alaska): The alert status was lowered to yellow on Saturday. The Alaska Volcano Observatory detected no more signs of eruptive activity at the summit lava dome since the small eruption on 18 May, and seismic activity has remained low. Surface temperatures detected via satellite data remain slightly elevated, but can be explained by the cooling of the lava dome.

Tungurahua (Ecuador): The Geophysical Institute warned that a new eruptive phase might be in the making at the volcano, which is one of the world's most active. Geophysical monitoring stations have been recording a significant, steady inflation (swelling) of the volcanic edifice. This is most likely a sign of new magma intruding at shallow depth. Seismic activity of the volcano has been generally low, with less than two earthquakes per day. Only some small earthquake swarms have been detected recently; such swarms are common in periods of quiescence and are associated with fluid movements within the volcano. Degassing of the volcano has also been at the lower end. However, this apparent calm could be deceiving: it might well be explained by a blockage of the conduit, not the absence of magma ready to erupt. The volcano has only been quiet since its last eruption in February-March this year, but its phases of calm have never lasted very long. In the last 8 years of activity, Tungurahua has had 15 similar quiet periods characterized by low seismic and degassing activity coupled with an inflationary deformation trend. In most cases, these quiet periods were followed by small to moderate eruptions, but sometimes also by violent, larger explosions. What makes it difficult for volcanologists to predict the next eruption is that clear precursory signs of new eruptions in the short term (hours to days) have only been detected in 20% of cases; many eruptions started very quickly at the volcano. In any case, based on the current seismic and geophysical observations and the volcano's past behaviour, a new eruption in the medium term (weeks to months) is considered very likely.