Big things at Santiaguito, Guatemala

A selection of the large eruptions that Santiaguito has produced in 2016. Left: 11 April (Source: INSIVUMEH). Middle: 19 May (Source: INSIVUMEH). Right: 17 June (Source: Stereo100Noticias).

Last week Anthony Lamur and I were back in Guatemala to collect more observations from Santiaguito volcano. The fieldwork was prompted by the occurrence of several very large eruptions at the volcano in 2016 (like those in the image above), a departure from the regular but relatively small explosions that are typical of the place. What we wanted to know was what mechanism is driving the much larger explosions?

Our campsite on Santa Maria on the morning of June 13th. The shadow of Santa Maria (3,772 m high) stretches far into the distance. 

Our task for the trip was simple: we would camp on Santa Maria and watch Santiaguito for a few days with optical and thermal cameras to record any explosions. We also deployed a temporary acoustic microphone to record the infrasound produced by the explosion. It turned out to be a whole lot more complex and difficult, mostly because of the rainy season. However, while we did not see any eruptions, we did manage to get glimpses of the vent and were woken up by a large explosion in the early hours of June 13th.

Santiaguito on the morning of June 14th. Close ups of the lava flows with pyroclastic flow damage, and the Caliente vent, are below.

What we saw during the few hours of visibility each day was very interesting. We could see clear evidence for the highly energetic and damaging nature of the explosions.

Close up of lava flows and damage from recent pyroclastic density currents on the south-eastern flank of Santiaguito. The dotted line marks roughly how close the coffee plantations get to the active volcano. Picture taken on 14th June. 

In the picture above, you can see the burnt trees due to the pyroclastic density currents generated during the larger explosive events. All the damage (that we could see) was on the south-eastern flank, and within a few kilometres of the vent.

Close-up of the Caliente vent at Sanatiguito. The vent is roughly 250 m wide, maybe up to 200 m deep. Picture taken on June 14th.

In the photo above, you can see what the vent looked like on June 14th. On any other volcano, this would look like a normal volcanic crater. But on Santiaguito, particularly when you compare with how it looked only a few months ago (see below), it has significantly changed. By my estimates, the crater is roughly 200-300 m wide, and up to 150 m deep, so a large amount of rock has been blasted away. This shows how energetic the recent eruptions at Santiaguito have been.

A comparison to show how much the vent has changed within 6 months. 

What did we learn? Well, you shouldn't camp on Santa Maria in the middle of the Guatemalan rainy season that's for sure. On a more serious note, we have seen how the large eruptions have affected the vent and the surrounding environment. We have also seen first hand how energetic the explosions must be.

It is difficult to predict what will happen at Santiaguito in the near future. Will the large explosions continue, and for how long? Will the dome deteriorate and eventually collapse? Or will the crater refill with a new plug of lava from below? One thing is for sure, we will be keeping a very close eye on this amazing volcano for the foreseeable future.

To learn more about the Liverpool Volcanology research efforts on Santiaguito, you can read my previous blog post about our recently published article in Geophysical Research Letters.