Co-eruptive deformation at Calbuco, April 2015

On the 22nd April Calbuco volcano, Chile, erupted for the first time since 1972, with very little warning. Plumes of volcanic ash reached heights of 16 km on the 22nd and up to 17 km in a second, longer duration eruption that began in the early hours of 23rd April.  A third eruption occurred on the 30th April with a ash heavy plume that reached heights of 5 km and lahars on the slopes of Calbuco.   Large volumes of SO2 were released during the first days of the eruption


Sentinel-1 interferogram showing subsidence at Calbuco during eruptions on the 22-23rd April 2015. Each full colour cycle represents ~2.8 cm of motion away from the satellite.

Several thousand people were evacuated from villages closest to Calbuco .   Ash fell over an area extending from the west coast of Chile to the east coast of Argentina, and grounded air traffic in Chile, Uruguay and Argentina.

There appears to have been only a very brief period of precursory activity before the 22nd April eruption.  No deformation was measured in Sentinel interferograms from the month before the eruption up until the 21st April.  The first co-eruptive interferograms (14th – 26th April) at Calbuco show subsidence on the western flank of the volcano of ~ 12cm.  The topography of the volcano’s crater has also changed, possibly due to ice melt as well as the eruption.

For more information about satellite observations of Calbuco, see the COMET webpage, here.

3 responses to “Co-eruptive deformation at Calbuco, April 2015

  1. Hi! I’m from near Calbuco volcano, and this was a pretty strange eruption, especially talking about precursory activity.

    About the interferogram, is it normal that the deformation covers a so broad area? Because a tiltmeter is installed about 4-5 km to the west. and no significant changes were detected before, and no comments were made after the eruption. My question is if, despite pointing to the Summit, the ground change could be registered due to the variation of tiltmeter position?

    Another thing: it’s common to see deformations away from volcanoes before eruptions? Sincé one can think it will occur beneath the mountain.

    My guess is that the inflation occured, or very slowly, or was there years before, but the lack of observations (others volcanoes were much more interesting) makes it difficult to answer.

    Nice article and I hope the “mysteries” of Calbuco eruption will be solved, particularly the short unrest before its reawakening.


    PD: I have a WP blog too about scientific topics (in spanish), here’s the url 😉

  2. Hi! Thank you for your comment!

    – The footprint of the deformation (~15 km diameter) is not unusual for co-eruptive displacements detected with InSAR. We don’t think that there was any deformation in the months before the eruption (at least no before 21st April).

    – There are actually quite a few examples of deformation happening several kilometres of more away from the associated volcanic edifice. But in this case, the fact that the displacements look like they are centred further to the west is likely to be related to the satellite geometry. SAR satellites are side-looking (incidence angle e.g., 30-40 degrees) and are sensitive to east-west displacements. The co-eruptive subsidence during the Calbuco eruption can actually be fit well by a deformation source beneath the volcano.

    We don’t know for sure whether there was a gradual inflation in the years before the April 2015 eruption – but I’m not aware of any evidence for it. There don’t seem to have been any geodetic precursors to the activity.

    Thank you for pointing me to your blog, you have lots of interesting information and discussion about the Calbuco eruption!

    Best wishes, Susi

  3. Thanks for answering. A couple days after my comment, Calbuco was raised again to yellow due to a sudden increase of seismic activity, and an inflation detected near it (apparently it came from the months before, no further details were given, except of the deformation magnitude in microradians), still in yellow at this time. I found a very interesting publication about Caulle using InSAR data that could help understand some points of Calbuco volcano. I’m preparing a post about it.

    Greetings from Chile

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