The volcano has become uncharacteristically calm. After the last large event on the 3rd Feb. we have seen very few small explosions. The gas flux has increased suggesting a less sealed system but seismicity still suggests there is magma moving but maybe very slowly. The photo shows the large ash cloud from the 3rd Feb. event taken from the city.
An eruption occurred in the early hours of the 18th Jan. and it has been heralded as one of the most dramatic night-time eruptions seen in recent years. Granted, it looks spectacular on the webcams de Mexico video. However, the explosion did not produce as much seismic energy as the larger events that occurred in 2005 (when there were no publically available images or social media). It is an interesting way to start 2017 and if the similarities with 2005 continue, we may see a lot more events like this and getting larger. There is clearly a large degassing magma body at depth and monitoring is currently critical. The only photos so far are from the reliable webcamsdemexico.com.
After trying to fly for several weeks, finally we managed to have the right conditions and 5 willing participants. After having measured high temperatures earlier in the month (highest temps. yet measured for this volcano) the temperatures were much lower with a maximum of only 320° C. This reflects the reduction in the effusion rate. The eruption is shifting from passive magma emplacement to the more common small Vulcanian eruptions occurring at least once per hour.
A flight over the volcano enabled us to determine that the dome was still growing, though at a very slow rate. The size of the dome had not increased by much, however, the surface temperature indicated active effusion.
The activity of the volcano has been showing a declining tendancy over the past weeks. Explosions are now of a smaller magnitude, releasing less ash with the columns not reaching such high altitudes. The SO2 fluxes are now getting harder to measure with only a small continuous gas release from the volcano. Fieldwork continues at CIIV, with the photo showing San Antonio, recently visited for continued studies of the PDC deposits that were produced during July 2015. You can see how erosion from the rain has cut a considerable channel already in the deposits. Only the top couple of metres were from the 2015 event, the rest being from material from older PDCs remobilized by lahars. This ravine received a smaller volume than the main deposit in Montegrade, with the flow jumping from one ravine to the other on a bend in Montegrande.