Entre 1-15 février, un total de 350 événements sismiques ou 21 par jour en moyenne ont été enregistrés, y compris 233 signaux de longue période interprétés pour être causée par des mouvements fluides, 8 séismes de longue période ainsi appelés tornillo, dont un a duré 148 secondes et 3 impulsions de tremblement volcanique (éventuellement indiquant les mouvements du magma).
L'activité visible consiste en des pulsations des colonnes de gaz des fumerolles atteignant 50-250 m de hauteur. [moins]

---
Source: GVP/USGS Weekly Volcanic Activity Report 7-13 March 2007

[moins]

<<Lascar in the Central Andes of Northern Chile started a new eruptive cycle on April 18th 2006, after almost one year of apparent repose (last eruption recorded in May 4th 2005). <br>After one week with several phreatic explosive cycles per day (some lasting up to two hours), reaching up to 3,500 m above the crater, the activity decreased. The ash collected in June around the crater area showed no signs of new magma, in agreement with seismic data (three seismometers were installed for one week, and one for nearly one month to record the seismic activity associated to the explosions). The volcano has continued its activity with several smaller explosions during May, July and August, although much more separated in time (up to several weeks). The last observed explosions occurred on June 12th at 16:00 hrs and August 14th at 18:00 hrs (local time, GMT-4)). The latter lasted for 5 minutes and the plume reached up to 450 m above the crater, and was rapidly dispersed towards the East-Southeast. This unusual long-lasting cycle of phreatic vulcanian explosions of Láscar volcano seems to continue, and efforts from the Chilean Geological Survey (Sernageomin) and the Chilean Emergency Office (Onemi) are under way to install permanent seismometers in the area.
Although no signs of new magma have been recognised so far, ascent of new magma in the future cannot be ruled out.>>

[moins]

"Lascar volcano ... started an eruptive cycle on April 18th 2006 at 11:35 hrs (all are local times). Four explosions were recorded on the 18th, one rose up to 3,000 m above the active crater. Two explosive cycles were observed on the 19th starting at 11:20 hrs and 13:21 hrs, the second being the largest rising up to 800 m above the crater. The plume, which essentially consisted in gases with little ash, was dispersed towards the north. Fine ash fell on the northern upper flank of the volcano within a radius of 3 km. Two new explosive cycles were observed on April 20th starting at 11:05 and 13:39hrs. The latter has been the longer observed so far, lasting 1 hour and 53 minutes. The plume consisted mainly of gases and little ash, rising up to 2500 m above the crater and dispersed towards the N at the beginning and at the end of the cycle towards the NE. Fine ash was deposited on the upper northern and eastern flanks.
Finally two new, but smaller, explosive cycles were observed today starting at 08:48 hrs and 11:42 hrs, lasting less than 15 minutes each, with an eruptive column rising up to 3000 m above the crater, similar to those of the previous day, but dispersed towards the westand SW, respectively.

These phreatic explosions show an unusual behavior of the volcano, and there is no evidence so far of new magma reaching the surface. Preliminary seismic data obtained by the Chilean Emergency Office (ONEMI) show only seismic events related to shallow degassing, without any seismic event associated todeeper fractures or magma movements."

[moins]

---
Background. Lascar is the most active volcano of the northern Chilean Andes. The andesitic -to- dacitic stratovolcano contains six overlapping summitcraters and lies 5 km W of an older, higher stratovolcano, Volcán Aguas Calientes. Lascar consists of two major edifices; activity began at the eastern volcano and then shifted to the western cone. The largest eruption of Lascar took place about 26,500 years ago, and following the eruption of theTumbres scoria flow about 9,000 years ago, activity shifted back to the eastern edifice, where three overlapping craters were formed. Frequent small-to-moderate explosive eruptions have been recorded from Lascar in historical time since the mid-19th century, along with periodic larger eruptions that produced ashfall hundreds of kilometers away from the volcano. The largest historical eruption of Lascar took place in 1993 and produced pyroclastic flows that extended up to 8.5 km NW of the summit.

Source: GVP/USGS Weekly Volcanic Activity Report, 4-10 May 2005

[moins]