It seems that (for now) this activity is phreatic, i.e. involves no fresh magma, only overheated water from the hydrothermal system, that can fragment rock into ash during explosive decompression. Temperature measurements gave a value of only 200°C at the vents. [less]

Both earthquakes related to rock fracturing and fluid movements have picked up in numbers and possibly indicate a new magmatic intrusion on its way. This scenario is confirmed by the start of small ash emissions and glow at the crater which is visible at night. The plume of gas and ash could be seen from space by the MODIS sensor, streching about 100 km to the southeast.
Copahue volcano had already experienced a first increase of activity in December, and a second one in January. No eruption followed and alert was lowered to green in April before returning to yellow again soon after. [less]

Weak seismic swarms continued to be registered mainly in the first week of February. A total of 331 seismic events were measured between 1-15 Feb. Degassing has been weak except on 5 Feb, when a gas plume rose significantly higher. [less]

The seismic swarm was accompanied by an increase in the degassing activity, creating a column of 500 m during pulses of more intense activity. No glow or ash emissions were seen. [less]

No ash emissions or incandescence, or other signs of surface activity other than a moderate slow increase in degassing have so far been observed. [less]

Until 09:56 local time (12:56 GMT) on 22 Jan, seismic activity had remained at low levels, both in occurrence of earthquakes, the energy released and the signal intensity of tremor associated with fluid movements inside the volcano. Then, at that time, there was a significant long-period (LP) earthquake and 3 hours later, shallow lower amplitude events started to occur.
At 13:20 local time, another LP earthquake of relatively strong intensity occurred and was followed by a seismic swarm with mostly long period events that continued for 20 minutes. [less]

Alert level remains at Orange because of the risk of sudden phreatic explosions. [less]

SERNAGEOMIN has lowered the alert level to yellow. ONEMI (Civil protection) maintains yellow alert for the community of Alto Biobio, mainly for the hazard of lahars. [less]

Only the alert level red remains in effect for the municipality of Alto Biobío because of the high risk of lahars in this area. [less]

The camera installed around the volcano, allowed to observe glow reflected in the clouds, and an area of ​​it in the active crater. The raise in tremor and the explosions also correlated with an increase of the gas column.
The eruptions of Copahue during recorded history are mostly small to moderate in size. One likely scenario are frequent phreatic or phreatomagmatic (generated by interaction of magma and water) explosions. Under these conditions, the main danger is from the fallout of pyroclastic material (ash fall and ballistic impacts in proximal areas). Larger explosions could generate pyroclastic surges and lahars. [less]

- From 10:45 local time, the seismic signal recorded at stations installed around the volcano Copahue showed a rapid increase and was characterized by strong low frequency tremor.
- The tremor signal correlated with an increase in the gas column, which turned black as ashes were erupted. The plume reached a height of 1.5 km and drifted about 13 km to the SW. [less]

It is apparently still a 'small' eruption, but the Alert Level for the volcano has been raised from GREEN to ORANGE. [less]

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