February 21 , 2016. EN. Cotopaxi , Momotombo , Shishaldin , Chiles/Cerro-Negro .
February 21 , 2016.
Cotopaxi, Ecuador :
Occasional increases in water vapor plumes, daily melting glaciers, lahars secondary and small internal explosion
Since the last report published on 29 January this year, the surface activity of the volcano Cotopaxi was mostly low . Such activity is characterized by the presence of water vapor in the crater, sporadics columns of gas emissions with a very low ash content. Currently, several of the monitoring parameters (SO2, LP type earthquakes, tremors, ash emissions, deformation) returned to their pre-eruption level base. However, the seismic activity of the volcano continues to record VT type events (~ 50 / day) and at least some internal explosions (1-3 / day).
Such activity could indicate the permanence of a source of pressure inside the volcano. According to the above, the most likely scenario, during a period ranging from days to weeks, is that the volcano surface activity remains at a low level. In this scenario, it may happen occasionally ash emissions, which may affect the surrounding towns of the volcano. On the other hand, secondary lahars whose presence within the limits of the National Park of Cotopaxi, similar to the previous month may also occur. Finally, an increase in internal and external activity of the volcano in the coming weeks is not excluded. However, this scenario is less likely.
The surface activity was characterized mainly by small gas emissions, low energy from the crater, sometimes reaching up to 600 m (Fig. 1), such as those that took place on 04 and 13 February at 7h43 and 7h37 TL (local time) and moved towards the northwest.
It is possible that increased precipitation on the slopes East of the cone contributes to increased the surface water of the hydrothermal system, facilitating increased frequency of fumaroles. The pluviometers of the IG – EPN installed on the East -North – East side of Cotopaxi, recorded a significant increase in rainfall in recent weeks.
In recent weeks, the seismic activity of the volcano Cotopaxi has not changed much from previous weeks. The volcano continues to present volcano-tectonic events (VT) with an average of about 60 VT / day, and a few small explosions and hybrid earthquakes. Most of these events have amplitudes of between M 0.5 and M 2.80 , and are under the crater between 1 and 13 km deep.
The results of GPS CAME (Cerro Ami) show a distortion pattern that was noticeable until the end of November 2015. From April to the end of November 2015, an accelerated movement with a tendency towards the West was observed. This trend was also observed on other GPS stations located on the Eastern flank. Subsequently, due to the weakening of internal stresses, it was observed that the deformation returned to a virtually stable level in the first weeks of 2016.
SO2 emissions remained below 1000 tons / day in recent weeks. The values obtained are almost at pre-eruptive base.
Since November 23, 2015, no significant ash fall associated with volcanic activity have been recorded. Small emissions of January probably did not produce measurable ash fall near the volcano.
Since August 28, 2015, several secondary lahars occurred on the Cotopaxi volcano. Unlike primary lahars that originate from contact with incandescent volcanic material with ice during large eruptions, the origine of secondary lahars is due to heavy rains that fall on the top of the volcano and drive downstream the ash deposited on sides during the eruptive phase that began on August 14, 2015. This initial mixture incorporating rocks and other debris is transported downstream increasing their energy in the slope .
Some of these lahars are also generated by snowmelt that occurs constantly. The anticipated volume of secondary lahars products by rain is much less important than by the major eruptions of Cotopaxi. Sometimes their peak flow reaches between 30 and 50 m3 / s, but in general, the throughput is lower and does not exceed 10 m3 / s. To date, there have been 58 secondary lahars, most of them descended from the Agualongo ravine located to the west of the volcano, and some by the North and East sides. Some days there were 3-4 episodes of lahar.
It is believed that most lahares currently produced by the fusion descended on the western slopes. In particular, thaws accentuate lahars generated in the afternoon. Current ice coverage of Cotopaxi is very cracked and weakened by this fusion that occurs continuously.
Photo taken on January 29, 2016, South flank of Cotopaxi, with the relief of Morurco left. Evidence of melting in this sector by the runoff of water at the end of the tongues of ice. (P. Mothes, IGEPN).
The monitoring data obtained until January 15, 2016 indicate that some monitoring parameters (SO2, tremors, ash, LP events) returned almost to pre-eruption level. All these parameters are related in some way at the gas outlet. The deformation of the volcano marks a pause since November 2015 and gradually returned to pre-eruption level. However, although these parameters are decreasing, earthquakes type VT, consistently detected since September 10, small explosions indicate that is still a source of pressure inside the volcano
One possible interpretation of this result set is that when the top of the magma intrusion becomes a low permeability cap it does not pass the gases, which accumulate to produce small internal explosion, as we have reported here. VT events might be interpreted as small movements of the cap or small magma resupplies whose volume does not change the model of stability that shows these stress values since late November. Currently, there is no evidence of a behavior change on Cotopaxi, regarding recent weeks, but we can not exclude the beginning of a change in stability in the short-term . The IGEPN is very attentive to any change in the conditions presented by the volcano.
Source : IGEPN
Photos : Igepn, paulytour.com.
Momotombo, Nicaragua :
The Momotombo volcano expels large amounts of magma .
20 FEBRUARY 2016. The Momotombo Volcano reported a loud explosion, which was highlighted by emanate large amounts of magma on its perfect cone, located north of Lake Managua, Nicaragua in the Pacific.
The magma expelled by the Momotombo covered almost the entire volcano, with a height of 1,297 meters. The National System for Prevention, Mitigation and Attention to Disasters reports of no damages to the population.
The director of Geology and Geophysics INETER, William Martinez, said at a press conference that the eruptive process at Momotombo presents no danger in the « short term » for the surrounding population to the colossus.
« With the levels that we are working not no danger to any population centers around the Momotombo volcano, » he said. Between Wednesday and Thursday Momotombo he experienced six loud explosions, according to government data.
The volcano is investigated by experts from INETER and Geological Survey (USGS), whom a contingent of experts from the UK will add, after the December 1 « awakened » after 110 years of being virtually asleep .
That perfect cone volcano once forced the transfer of the city of Leon in 1610 and its activity in 1886 made obscure western Nicaragua for 23 days, according to records of INETER.
Source : Antena 3
Photo : diariocorreo.pe
Shishaldin, Alaska :
54°45’19 » N 163°58’16 » W,
Summit Elevation 9373 ft (2857 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW
The level of seismic activity has changed little over the past week and remains above background levels. The ongoing seismic activity is characterized by low-level seismic tremor, small discrete events, and very small explosions. No activity was observed in mostly cloudy satellite images this week.
Shishaldin volcano, located near the center of Unimak Island in the eastern Aleutian Islands, is a spectacular symmetric cone with a base diameter of approximately 16 km (10 mi). A 200-m-wide (660 ft) funnel-shaped summit crater typically emits a steam plume and occasional small amounts of ash. Shishaldin is one of the most active volcanoes in the Aleutian volcanic arc, with at least 54 episodes of unrest including over 24 confirmed eruptions since 1775. Most eruptions are relatively small, although the April-May 1999 event generated an ash column that reached 45,000 ft above sea level.
Source : AVO
Photo : Read, Cyrus ( 2008)
Chiles et Cerro Negro , Colombia :
Subject: Bulletin activities of volcanoes Chiles and Cerro Negro.
The level of volcanic activity is maintained at level: YELLOW or (III): changes in the behavior of volcanic activity
About the monitoring of the activity of volcanoes Chiles and Cerro Negro, the Colombian Geological Service reports that:
Compared to the previous week, the daily presence of events showed a decrease from 152 to 106 earthquakes. Seismic activity continues to be dominated by events related to rock fracturing. However, some events whose the characteristics indicate a fluid movement are highlighted. The vast majority of earthquakes were located at distances up to 4 km in the southwest sector of the Chiles volcano, with depths between 0.5 and 9 km of the volcanic peak. The calculated maximum local magnitude was M1,0 on the Richter scale. Temperature values recorded in the hot springs area of Baño Grande remain stable, with an average value of 43 ° C.
The trend of low levels of seismic events is maintained. However, it is possible to see the occurrence of earthquakes of energy that could be felt by residents in the volcanic influence. The SGC-OVSP and IGEPN closely follow the evolution of the volcanic phenomenon and promptly notify the changes that are detected, particularly those that demonstrate a probable eruption.
Source : SGC.
Photo : Ingeominas.