The Mayon alert level has been lowered to 2 / moderate level of instability.
The daily control of the volcano revealed:
- a general decrease in seismicity
- a deflation since 20 February
- current SO2 concentrations reflect decreasing gas volumes from unregenerated magma beneath the building as well as cooling lava deposits on the summit and volcanic slopes.
- since March 18, no lava flows have been observed; incandescence has decreased, and gravitational lava flows have stabilized ... these factors are compatible with a cessation of magmatic input to the surface.
The permanent danger zone of 6 km is still to be avoided, and the inhabitants of the drainages are invited to remain vigilant.
VAAC Tokyo has been reporting ash emissions for the past few days in Suwanose-jima.
The images of the JMA webcam also show incandescence, and ash emissions.
Sources: JMA & VAAC Tokyo
The activity level of Sabancaya in Peru remains moderate, with for the week of March 19 to 25, an average of 17 daily explosions, accompanied by plumes rising up to 2,700 meters above the crater and dispersing to a SW sector.
On March 28, the IGP reports a lahar, beginning at 11:13 am, descending the southeast flank of the volcano, towards the Rio Sallalli. The seismic station recorded its activity during 3h 40 minutes, and qualifies it of dimensions smaller than that of March 13th.
Source: IG Peru
Sernageomin informs, in its special report of volcanic activity, of the recording of a volcano-tectonic earthquake of ML 3.1 and a depth of 3.6 km. at the Mocho-Choshuenco Complex, located in the southern Andes on March 28 at 8:35 local / 11:25 GMT; this kind of earthquake is associated with rock fracturing.
The volcanic alert remains however in Verde.
Mocho-Choshuenco complex - Volcán Mocho (left), Choshuenco (right) Puerto Fui and Lago Pirihueico (in the foreground). - picture Avodrocc
The Mocho-Coshuenco complex consists of two twin stratovolcanoes, covered with glaciers. They are dated from the formation at the end of the Ice Age of a 4 km wide caldera in which they settled.
Parasitic craters and basaltic slag cones punctuate the NE and SW flanks of the complex.
The small Choshuenco dates from the end of the Ice Age, and produced a major Pliny eruption 10,300 years ago, which is responsible for the Neltume pumice. (GVP)
El Mocho, from andesitic to dacitic, dated to a postglacial age, was historically active in 1864 and 1937.
Summary of the explosive history from Mocho-Choshuenco since deglaciation (~ 18 ka). Each unit is represented by its age probability distribution determined using Bayesian analysis of radiocarbon data, the height corresponds to the approximate magnitude (dashed lines used where magnitude is not well constrained) and the colour corresponds to the average SiO2 glass composition. Magnitude = log10[eruption mass (kg) − 7] (Pyle, 2000). The erosion rates, temperature, humidity, climate and vegetation densities are inferred from the interpretations made on the Lago Puyehue core (ca. 90 km south of Mocho-Choshuenco; Bertrand et al., 2008; Vargas-Ramirez et al., 2008).
- Sernageomin - Special report of actividad volcanica, Los Rios region, C.V. Moche-Choshuenco - link
- The frequency and magnitude of explosive post-glacial eruptions at Volcán Mocho-Choshuenco, southern Chile - by H.Rawson & al.- link
- Global Volcanism Program - Mocho-Choshuenco
The New Zealand Defense Force / NZDF flew over the Ambae volcano at the request of the GNS.
GNS reports that eruptive activity has increased over the past 10 days, with ash falling and acid rain affecting crops, water supplies and some buildings.
For the period from March 21st to 27th, ash plumes emitted by the Lombenben reached heights ranging between 3,000 and 4,600 meters asl, mainly drifting south and southwest, before affecting north and west zones end of the week.
The importance of ash falls is illustrated by "before and after" photos.
The Monowai submarine volcano, in the north of the Kermadec arch, was also the object of a surveillance flight, following an increase in its seismic activity.
Sources: newsie.co.nz & Penama Adventist College