Roundup of Global Volcanic Activity:
Churchill (United States, Eastern Alaska): A seismic swarm with magnitudes up to 3.5 has been occurring in the Wrangell Arc about 40 km NE of Mt. Churchill volcano during the past few days. The intensity and frequency of the quakes has calmed down yesterday. While some few of the quakes are near the volcano, most are not, and the swarm is probably not linked to the volcanic system of Mt Churchill volcano.
Long Valley (California): Normal seismic activity with numerous tiny earthquakes continues to occur at the southern and western parts of the caldera as well as under Mammoth mountain. There are no signs of a possible eruption in a near future.
Colima (Western Mexico): Although the volcano is no longer making much news, a lava flow continues to effuse as a viscous flow on the upper eastern flank of the volcano.
Popocatépetl (Central Mexico): Activity has been comparably low with an average of 1-2 emissions of steam and gas, sometimes some ash, per hour during the past days. The strong explosion from 12 July has effectively destroyed the new lava dome, an aerial inspection via helicopter on 15 July showed. In the past 24 hours, a number of volcanic-tectonic quakes have appeared, which could indicate that a new batch of magma is currently intruding, and lead to another phase of increased activity soon. The alert level remains unchanged at Yellow Phase 3.
Santa María / Santiaguito (Guatemala): Not much has changed in the generally weak activity. Occasional explosions, sometimes moderately large, occur at irregular intervals. One yesterday morning at 05:59 local time produced an ash plume of 700 m height and ash fall in areas to the SW. The lava flow on the southern flank of the dome remains active and produces small rock avalanches.
Pacaya (Guatemala): Mild strombolian activity from the Mackenney crater continues.
Fuego (Guatemala): The lava flow on the southern side has remained active and was about 250 m long this morning, producing near-constant rockfalls towards the Taniluya canyon. At the summit, there are occasional strombolian explosions with incandescent material ejected to 100-125 m height above the crater.
Telica (Nicaragua): The swarm of small earthquakes continues with little changes over the past days.
San Cristobal (Nicaragua): Some elevated seismicity was recorded at the volcano during recent days and continues. This includes phases of harmonic tremor and long-period events.
Turrialba (Costa Rica): The seismic swarm continues but has decreased in strength during the past day.
Tungurahua (Ecuador): After the strong vulcanian explosion on 14 July, the volcano calmed down first, but resumed activity on 16 July which has been characterized by ash venting and small to moderate explosions and is continuing. This activity was accompanied by the appearance of tremor and long-period earthquakes indicative of fluid movements. In addition, inflation is measured at the NW flank, suggesting that more magma is rising, and could lead to new powerful explosions similar to the one from last Sunday.
Sabancaya (Peru): A strong seismic swarm has occurred during the past days under the volcano, culminating in a magnitude 5.9 earthquake on 16 July. The swarm consisted almost entirely of volcanic-tectonic quakes, that relate to rock fracturing due to rapid pressure changes and might be caused by an intrusion of magma. IGP reports that up to 1500 earthquakes were recorded per day. At the moment, the swarm still continues, but is decreasing. No changes of activity have been noticed at the surface. The number of long-period quakes (thought to correspond to internal movements of magma, gasses and other fluids) has remained low.