Chapter 11: Santa Maria (Guatemala)

Watch out for the quiet ones.

They often are overlooked until internal pressures reach the breaking point and they explode.

Santa Maria, in Guatemala, is a case in point.

Geologists suspect that this volcano spent about five thousand years building up its beautiful pyramid shape. Afterwards, it probably rested for some twenty-five thousand years, apart from rare little lava flows now and then. (Berry et al.; MTU)

Then, on October 24, 1902, Santa Maria blew out most of its southwest flank in one of the largest eruptions of the twentieth century, devastating southwestern Guatemala and killing over eight thousand people quickly during the eruption as well as thousands more, later on, through disease and famine. (Ball; Berry et al.; Brown et al.; De Angelis et al.; Oppenheimer)

An unknown photographer caught the 1902 eruption the next day, when Santa Maria was tapering off. (Image: Wikimedia, Spanish, public domain)

The Santiaguito dome complex

In 1922, after a twenty-year sleep, Santa Maria woke up again and began to fill in the huge southwestern crater with a lava-dome complex that people now call Santiaguito.

The domes collapsed in 1929, causing a big pyroclastic surge; casualty estimates vary from a few hundred to as many as five thousand deaths from that disaster. (Brown et al.; De Angelis et al.)

Ever since then, eruptive construction work at Santiaguito has continued almost nonstop and, fortunately, without further regional catastrophes, although people nearby occasionally do die in lahars or pyroclastic flows. (Brown et al.)

Fernando Reyes Palencia, CC BY-SA 3.0)

Today, Caliente dome is the currently active vent there, while the rest of the huge Santa Maria edifice is quiet at the moment. (De Angelis et al.)

This is one of the few active volcanoes where, because of the geometry of the 1902 blast, you can look down on an eruption, some four thousand feet below your feet (while standing on Santa Maria’s summit).

Volcanologists love that, and so do tourists.

This videographer starts in with a close-up of Caliente dome just before it erupts (see the subtle changes as the ground inflates?), and then widens the angle to catch all the details, including a small pyroclastic flow that stays on the dome.

Caliente has these small to moderate explosions hourly or every few hours, as well as occasional big blasts that generate considerable ashfall and lethal pyroclastic flows on nearby slopes, some of which host farms and coffee plantations.

Its explosive moods — including a rather extreme period (for Santiaguito) from 2014 to 2016 — alternate with quieter spells like the current one, when a more effusive (lava flow) eruption style predominates. (Brown et al.; De Angelis; De Angelis et al.)

Even when things are fairly quiet at the dome complex, its loose volcanic ash frequently flows down river drainages in damaging lahars, especially during the summer rainy season, forcing evacuations and sometimes threatening a crucial bridge on the Inter-American Highway that links countries along the Pacific coast.

The worst event recently was when lahars destroyed the town of El Palmar (link is in Spanish) — just a few miles from Santiaguito — twice, once in the 1980s and again in 1998, when it was finally abandoned. (De Angelis et al.; Newhall, 1999)

Santa Maria and the Decade Volcano program

Francisco Sandoval Guate/Shutterstock

Santa Maria was chosen as a Decade Volcano because of that powerful blast in 1902, the variety of ongoing hazards, and the presence of hundreds of thousands of people living and working around the volcano both in rural areas and in the neighboring municipality of Quetzaltenango. (De Angelis et al.; MTU)

Unfortunately, civil unrest and related factors during the 1990s limited program work here. (European Volcanology Society; Newhall, 1996)

As volcanologist Chris Newhall wrote in 1999 (link added):

A well-attended workshop in November 1993 generated much enthusiasm and many plans. Regrettably, support from higher levels of the government was not forthcoming and disappointingly few of the plans have been implemented.

International support in the 21st Century

There is a Santiaguito Volcano Observatory (OVSAN, in Spanish) now. It’s located about four miles from Caliente and operated by the National Institute of Seismology, Volcanology, Meteorology, and Hydrology (INSIVUMEH).

However, until very recently the highly motivated, hard-working observatory staff could only keep an eye on the dome complex during daylight hours and they had no real-time data feed, although some information from a few seismic instruments at Santiaguito reached INSIVUMEH headquarters in Guatemala City, 70 miles away, via telemetry. (De Angelis; De Angelis et al.)

This is not an ideal way to monitor a volcanic complex near people that erupts around the clock and is prone to sudden deadly lahars and pyroclastic flows — but no resources existed for an upgrade.

As the years passed, though, state-of-the-art volcano monitoring equipment came into widespread use at many of the world’s monitored volcanoes, and its cost dropped accordingly. (De Angelis et al.)

In 2018, noting that Guatemala’s 3G cellular network could support monitoring data transmission, the organization Geoscientists Without Borders funded an international and locally based project to establish real-time seismic and infrasound monitoring of Santiaguito, to deploy software for routine analysis of the data, and to train INSIVUMEH personnel and young Guatemalan scientists in the system’s use and maintenance. (De Angelis; De Angelis et al.; GWB)

By the end of August 2021, all of the project’s objectives had been accomplished — with four seismic stations instead of the two originally proposed!

Santa Maria’s Santiaguito dome complex now has its first broadband seismic network. A baseline earthquake catalog exists, and other projects building on these initial successes have been funded by USAID, the European Union, various international agencies, and collaborating Guatemalan universities. (GWB)

Volcanologists now pick up numerous lahars, explosions, and pyroclastic flows at Santiaguito. The data may soon lead to a lahar early warning system. Geophysicists can also use the information to model Caliente’s formerly mysterious transitions between explosive and effusive eruption “moods.” (De Angelis)

If all continues to go well, the new monitoring network at Santiaguito will eventually serve as a basis for a planned bigger system aimed at providing both early warning and real-time alerts of Caliente’s ongoing/impending activity, particularly its lahars and pyroclastic flows. (De Angelis)

Would all of this have come to pass without that initial enthusiasm and the hopeful but thwarted plans made at Santa Maria during the International Decade?

It’s hard to say. The important thing is that Santa Maria’s human neighbors have a little more security, now that a basic monitoring network and trained personnel are in place.

Come what may, this Decade Volcano will not catch them by surprise the way it did a century ago!


Location: 14.757° N, 91.552° W, in Quetzaltenango Department, southwest Guatemala. The GVP Volcano Number is 342030.

Nearby Population:

Per the Global Volcanism Program:

  • Within 5 km (3 miles): 8,675.
  • Within 10 km (6 miles): 119,462.
  • Within 30 km (19 miles): 1,259,600.
  • Within 100 km (62 miles): 6,197,420.

Current Status:

In its December 2022 bulletin (via machine translator), INSIVUMEH reported:

The volcano maintains a high activity due to the extrusion of lava in blocks in the dome of the Caliente Dome in a West-Southwest direction and the unstable material in the crater, there is a probability of moderate to strong pyroclastic flows, so you should not stay near or within the riverbeds near the slopes of the volcano.

The Global Volcanism Program page also carries recent activity reports.

Biggest recorded event: 1902, VEI 6.


The National Institute of Seismology, Volcanology, Meteorology, and Hydrology (INSIVUMEH).

Washington VAAC (if any messages have been issued in the last 15 days)

Live webcam views of Santiaguito are hard to find, but if any come online, they will probably be embedded here.

Meanwhile, in Antigua, Guatemala, they dance to music inspired by a 1902 earthquake disaster that occurred six months before Santa Maria exploded. Coincidence? No one know for sure.

Soon now, with the revised Decade Volcano eBook — in the next two to three weeks, if all goes well.

Featured image: Simon Dannhauser/Shutterstock



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