What's up at Colima?

Or rather, what went down at Volcán de Colima? Nearly two weeks ago the Mexican volcano experienced an intense phase of activity that prompted evacuations from local settlements and closed the nearby national airport. Now that the activity seems to have calmed down (relatively), I wanted to summarise what we know and discuss the possible implications it has for the future of the volcano.

Incandescent rockfalls seen descending the flank of Volcan de Colima early on the 10th of July, not long before the first of the major pyroclastic flows later that day. Image credit: webcamsdemexico.com

What happened?
Here are the facts. Prior to the paroxysmal phase on the 10th of July, there was a lava dome rapidly growing inside the summit crater. Incandescent rockfalls from the overflowing dome (see above image) and frequent small explosions were a common sight. All of which was typical activity for a volcano which has been almost continuously erupting since November 1998 (with the exception of a 18 month pause from 2011 to 2013).

Dramatic image of ash rising from one of the pyroclastic flows on 10th July at Volcan de Colima. Image credit: Tapiro Fotografia. 

On Friday the 10th of July, a series of massive pyroclastic flows streamed from the volcano and produced ash plumes up to 7 km high. A local webcam managed to capture the scene as one flow made its way down. The plumes scattered thick ash over the surrounding countryside and villages. The flows deposited hot ash and giant boulders nearly 10 km away from the volcano, the largest such flow at the volcano for over 100 years. With the first clear views of the summit, it was clear that its shape had changed significantly during this sequence of activity. The summit had become unstable and collapsed, producing the pyroclastic flows.

The grey 10 July pyroclastic flow deposits tracing a path from summit to where it eventually ran out of energy, nearly 10 km in distance. The new black lava flow can also be seen descending from the summit. Photo credit: Tom Pfeiffer/Volcanodiscovery. 

Immediately afterwards, a brand new lava dome began growing inside the reshaped summit crater. From the new dome, a lava flow descended the south flank of the volcano, in the same direction as the pyroclastic flows. Satellite images taken on the 18th of July captured the whole scene, including the path taken by the pyroclastic flows. Glowing rockfalls frequently descended from the front of the flow and from the new lava dome at the summit (see picture below). The lava flow has, at the time of writing, reached nearly 1.5 km from the summit and seems to have slowed down considerably in the past few days.

The new lava flow (middle right) flowing from the lava dome growing on the reshaped summit at Volcán de Colima. Incandescent rockfalls can be seen coming from the front of the lava flow as well as the summit lava dome. Photo credit: Tom Pfeiffer/Volcanodiscovery.

Thankfully, no fatalities or injuries have been reported and the pyroclastic flows did not reach any of the local settlements which had been evacuated. Unfortunately, local farmland has been damaged and some cattle were burned by the hot deposits left by the pyroclastic flows. Additionally, a number of monitoring stations were destroyed by the intense and powerful flows. I am relieved that no-one was attending these stations when the pyroclastic flows came down!

A close-up of the bottom part of the deposits left by the pyroclastic flows. It is very fortunate that the power pylons were not knocked over by the flows.  Photo credit: Tom Pfeiffer/Volcanodiscovery.

What next?
For now, the major concern will be what happens to all the loose, hot material left behind by the pyroclastic flows. This material, combined with the current central american rainy season, will lead to the formation of lahars: fast-flowing, debris-filled mud flows which can wipe out anything in their path. John Stevenson has an excellent blog post with spectacular videos of lahars that he witnessed at Colima in the summer of 2007 (it's also worth noting that the location he recorded the videos was overwhelmed by the pyroclastic flows on July 10th).

The deposits of the pyroclastic flow, prime material for forming destructive lahars. The volcano is sitting in the clouds in the upper left. Photo credit: Tom Pfeiffer/Volcanodiscovery. 

The other concern this activity raises is whether this brings the volcano one step closer to a more major eruption, or what we volcanologists call a 'Plinian eruption'. On January 20th 1913, Volcán de Colima erupted in this style, producing a 20 km high ash plume and unleashing enormous pyroclastic flows down its flanks. The eruption shaved 100 m off the height of the volcano and produced a crater 350 m deep and 450 m wide. Since 1998, the volcano has been displaying very similar activity to what was described in the years prior to 1913.

Volcán de Colima, before (left) and after (right) the 20th January 1913 Plinian eruption. Adapted from  Breton Gonzalez et. al. 2002. 

Now, here comes the speculation from me. Firstly, I think the original dome was unstable because of the more intense explosive activity the volcano had been experiencing since January (for example). Secondly, I think the removal of the material from the summit has probably relieved a little bit of pressure from inside the volcano. Its like slightly opening a bottle of fizzy drink, letting a little bit of air out so you can open the bottle without spilling its contents everywhere. Only here, the bottle has been opened for just a moment and the pressure inside may be slowly building up again. However, as Josh Hayes nicely summarised in his excellent blog post about this activity:

"At this stage it is difficult to determine whether Volcán de Colima will indeed become Plinian, and so it is important that we recognise that it is not a certainty. However, given what the 1913 eruption could do today, it is important to recognise what could potentially occur to develop appropriate preparedness plans."

As always, I will be keeping a close eye on any developments from Volcán de Colima. If you would like to watch as well, you can check out the webcam for live images.

Thank you to Tom Pfeiffer for his permission to use some of his amazing photos for this post, you can see more on the Volcanodiscovery website.