Popocatépetl Update

There is my favorite volcano — “Smoking Mountain,” in Aztec — standing tall between the city of Puebla and the sunset. (On the other side of the mountain, in Mexico City, they take equally beautiful pictures of the sunrise.)

I’m posting this now because it has made the news with an impressive explosion on the 24th and I think it might be helpful to put that in context — Mexican volcanologists expect such activity as part of the current Yellow, Phase 2 alert status.

If and when that level is raised/lowered, you will find the official news here (Spanish).

It was quite impressive:

In their update the next day, CENAPRED called this “moderate.”

They were right, when you compare that to some of the blasts that have occurred during this long-lasting eruption, which began in 1994:

A few highlights found on a YouTube search:

As I’ve noted before, Popo is dangerous.

Fortunately, it also has an open conduit. This has kept things at a somewhat lower intensity over the years than they might have been.

Since Decade Volcanoes Colima (Mexico) and Merapi (Indonesia) have open conduits, too, I’ve been reading up on it recently with papers like this.

Most of that sort of material gets into too much technical detail for a lay reader, but a little of it has sunk in a bit.

Here’s what I think is going on:

  • There’s lots of magma down there, but it’s not rising quickly.
  • As it inches up the conduit, most of its dissolved gases, which power explosions, escape and quietly leave the volcano through the open vent.
  • When the degassed magma finally oozes out, it just piles up into a lava dome.

    Exhibit A is from another subduction-zone volcano, Mount St. Helens, 2004-2008.

  • This is oversimplification to the nth degree, but nonetheless basically correct, I think: Summit lava domes can plug the conduit. Gas pressure builds up and eventually blows up the dome. This is what Popo has been doing now for decades, and most recently this past week in that moderate explosion.

    Mount Merapi, over on the island of Java, does this so often, with the dome either collapsing under gravity or exploding, that it’s known as a “Merapi-style” eruption (of note, Popo doesn’t fit this perfectly since it isn’t showing the usual accompanying pyroclastic flows):

    Business as usual, day in, day out, at Mount Merapi — most of the time. (The exceptions are bad, as we’ll see in the next bullet point.)

  • Even more troublesome than a dome failure is when a fresh batch of gassy magma comes in and rises quickly. There isn’t time for degassing and you get a big explosive eruption.

    From what I’ve understood of the reading, this happened at Merapi in 2010 — starting with a big blast at around 1700, an hour before this rescue mission happened:

    They are trying to get the volcano’s spiritual gatekeeper, Mbah Maridjan, off Merapi.

    As you see, he stayed and so did 34 others who refused to take his advice and leave. In Mount Merapi’s previous dome-forming eruptions, this village, though just a few miles from the summit, had always been a safe distance away from the flow channels.

    Circumstances were different this time, and a pyroclastic surge came through about an hour after the rescuers left, killing all 35 people.

We need to expect the unexpected at any erupting volcano — and to follow expert advice during an emergency.

But we don’t need to live in mindless fear. Warnings and evacuations before and during Merapi’s unexpectedly large eruption in 2010 saved tens of thousands of lives.

Popocatépetl is carefully watched, too.

Its big explosion on February 25th drew headlines but was not the end of the world, even though the volcanologists’ report did not get equal attention.

I don’t think they mind, as long as the people who are at risk take them seriously.

When the volcano is violent, everyone listens.

But when it has been quietly building a new dome for a while, people occasionally ignore the exclusion zoning and go up there.

Some are lucky, like whoever took that 2015 video in the highlights compilation; others, not so much.

Anyway, all the volcanoes we’ve mentioned are closely monitored, and here are their Global Volcanism Program pages with more information and updates:


Meanwhile, on La Palma in 2021…

Featured image: Dejan Jovanovic/Pixabay.

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