Gamkonora volcano (Indonesia): seismic swarm triggers eruption alert
Increased earthquake activity has triggered an eruption alert by VSI, who raised the volcano's status to 3 ("Siaga", "warning") out of 4 this morning. Indonesian volcanologists reported that the degassing plume from the summit crater of the volcano has turned dark, which suggests the presence of ash (probably phreatic in origin) since 25 May.
The seismicity has shown significant changes with the appearance of harmonic tremor, low-frequency "tornillo" type-earthquakes (known from Galeras volcano in Colombia to often precede explosions). Volcanic-tectonic quakes (VA-type) related to rock fracturing have increased a lot, suggesting that magma at depth is intruding into new dykes.
No ash plumes have been detected on satellite images. The last activity of Gamkonora goes back to January, when it produced some small phreatic explosions.
After last week's intense ash eruptions generating plumes 2-3 km high, Gamkonora volcano has quieted down over the past days. Since July 13, seismicity has decreased sharply and no new larger ash eruptions have occurred since then.The Indonesian Volcanological Survey has lowered the alert level and many villagers who had been evacuated from the slopes of the volcano have returned home.... [meer...]