Iya volcano (Flores): seismic unrest, alert level raised
The Indonesian Volcanologic Survey raised the alert level of the stratovolcano from 1 (lowest) to 2 ("waspada", watch) yesterday evening. The decision came as increased seismic activity had been detected under the volcano, possibly related to a new magma intrusion that could be precursor of a new eruption.
Fri, 30 Sep 2016, 17:1717:17 PM | BY: T
A seismic swarm began at 15:30 local time on 29 Sep; within 18 hours, 8 relatively large tectonic earthquakes of magnitudes around 5 and 17 volcano-tectonic quakes were recorded while the normal averages are only 6-14 tectonic and 4-8 volcanic quakes total for a month. Presumably, at least some of the quakes have been caused by magma pressurizing rocks and fracturing them at depth.
In historic times, Iya volcano has erupted at least 8 times, last in 1971, and it is one of Flores'most active volcanoes. Most explosions were small to moderate phreatic and phreatomagmatic events, i.e. (partially) driven by steam explosions of ground water in contact with magma. Iya's largest eruption occurred on 27 Jan 1969 and measured VEI 3, producing a violent explosion with pyroclastic flows.
In connection with the observed increase in volcanic activity, which might or might not lead to new eruptions in the near to medium term future, local people and tourists are advised to avoid the area of the crater.
Wed, 28 Sep 2016, 06:00
Iya volcano (Flores Island, Indonesia) - Smithsonian / USGS Weekly Volcanic Activity Report for 28 September-4 October 2016 (New Activity / Unrest)
PVMBG reported that during 1 July-29 September variable-density white plumes rose as high as 150 m above Iya. During most of that period seismicity was at normal levels characterized by deep and shallow volcanic earthquakes each detected at a rate of less than 10 events per day. Between 1550 and 1800 on 29 September, however, the seismic network detected 17 volcanic earthquakes. ... Read all