Earlier today the authorities in Chile raised the alert lever for Copahue to level Red. This was prompted by an increase of seismic signals such as low frequency magmatic Earthquakes. A sign of the pressure rapidly increasing inside the volcano.
The authorities have declared that the exclusion zone will be increased to 25 kilometers from the volcano, and that 2200 people will be evactuated.
Copahues crater contains a highly acidic lake (Copahue means Sulphur Lake in the local language) and the eruptions during the last hundred years have consisted of pyroclastic flows and acidic lahars. During the eruption in 2000 the lake emptied out, but rapidly grew back to normal levels. Technically Copahue is a stratovolcano (thank you Karen for pointing out my mistake) sitting on the flank of a large caldera measuring 22 by 18 kilometers. Technically this make it into a Somma volcano, one of the more explosive types of caldera volcanoes.
Sofar the activity at Copahue has been mainly steam from the lake as it dries up, gas emissions and now a continous phreatic detonation. The alert level was last raised to yellow on the 8th of may.
Here is the direct conclusion by Gil Fernando Cruz at Sernageomin about what will happen:
The intensity and type of seismicity observed in recent days, in conjunction with the deformation of the volcanic edifice, suggest, with a high probability, that the rise of a magmatic body in the shallow layers of the volcano has entered a process of no return. It is highly probable that an extrusion of a dome and its associated phenomena such as explosive phreatic events, magmatic eruptions and a vulcanian type and/or a subpliniana eruption, with intensities greater than seen before might occur. Such eruptions could generate pyroclastic flows and lahars. It is recommended to focus on a radius of 15 km around the active crater and on the banks of the rivers originating in the volcano at the possibility of lahars. The previous alert level is therefore changed to RED.
More will be added to this post as things unfurl. There will also hopefully be a few added links.
Research paper on Copahue: http://www.wesleyan.edu/ees/JCV/Varekamp-407-15.pdf