At some point in the mid-sixth century C.E., a volcano erupted in what is today El Salvador. When exactly Tierra Blanca Joven exploded remains controversial, but it is agreed that the blast was powerful. Among other things, it may have caused a cold spell in the northern hemisphere, and is believed to have contributed to the ultimate decline of the Maya.
But whenever exactly Tierra Blanca Joven blew, a new paper published in the journal of Antiquity by Akira Ichikawa of the University of Colorado Boulder and Nagoya University suggests that when the stricken area in El Salvador was repopulated, people at the site of San Andres used the volcanic ejecta to construct a pyramid standing on a platform.
Then when another volcano blew in the 7th century, they erected even more monumental public buildings. There is no evidence of monumental construction at San Andres before these two eruptions.
Ichikawa sees this drive to rebuild, and monumentally at that, as testament to human resilience and creativity in the face of abrupt environmental change.
'Devastated by tephra'
The eruption may have been the largest Central America experienced during the Holocene, the current post-ice age geological epoch. It may even have caused cooling throughout the northern hemisphere, though there are timing issues – the correlation between the tentative dating of the eruption and the cold spell not clear-cut.
Regarding the timing and magnitude of the eruption, a paper published in PNAS in October 2020 proposes that it happened in 431 C.E., with a margin of error of two years – which is some years before the northern hemisphere temperature anomaly. That paper also posits that eruption was indeed mighty but not cataclysmic, and that its ash and pyroclastic flows mainly impacted populations within 80 kilometers of the volcano.
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Even if so, San Andres is about 40 kilometers from Lake Ilopango, which formed in the volcano’s caldera. The valley housing San Andres was certainly “devastated by tephra” (ejected rock) from Tierra Blanca Joven, which accumulated to half a meter thick at the site.
The goal in his research at San Andres was, Ichikawa explains, to investigate how the eruption affected the local and broader Maya civilization.
So, when did the volcano blow, and then what happened? Ichikawa doesn't rule out a date around 431 C.E., but suggests it possible that the eruption was later, in about 539 or 540 C.E. The debate on the timing is not closed, he stresses. The radiocarbon dating techniques pinpointing the date of the Ilopango eruption are "a bit tricky" because the calibration curve for the radiocarbon date is flat between 400-550 C.E., he explains.
Radiocarbon dating of matter in the pyramid and platform indicates dates of 545 to 570 C.E. If the Tierra Blanca Joven eruption really occurred in 431, this indicates that it took people a century to return, and reconquer the volcano-blasted land. If the eruption was in 539-540 B.C.E. then they came back quite fast.
More investigation wil be needed to reach clearer conclusions when Tierra Blanca Joven eruption actually happened, Ichikawa says.
In any case, whether people returned while the lava was spanking new or after as much as a century, Ichikawa posits that the vast project of erecting the monumental buildings was crucial to reestablishing the social and political order in the region.
And monumental they were. The platform from which the pyramid arose measures 85 meters in length by 65 meters in width and 7 meters high. The pyramid is 35 by 40 meters in base area and 13 meters high. Together the platform and pyramid are called the Campana Structure and measure a vast 33,000 square meters in volume, Ichikawa writes.
Based on archaeological investigation beneath the volcanic tephra, Ichikawa concludes, San Andres had no monumental construction before the eruption – despite the fact that the region had been occupied for at least 3,000 years, separate work has shown.
Then another volcano blew
Some decades after the construction of the pyramid and platform, there was another eruption, much closer to home: six kilometers from San Andres, in the year 620 C.E. The Loma eruption was smaller in magnitude but also showered ash and tephra on the site.
Archaeologists have identified adobe construction post-dating the Loma eruption and postulate that some other monumental features at San Andres, including an adobe and mud acropolis, date to after the Loma eruption as well.
If anything, the locals seem to have built even more grandly: the acropolis is over 91,000 square meters in volume, almost three times that of the Campana structure (platform and pyramid).
In any case, the bottom line is that the site didn’t feature monumental construction before these eruptions: The first was after the Tierra Blanca Joven blast, and more followed the Loma eruption. That has to mean something.
Based on pottery evidence indicating continuity, Ichikawa postulates that the site was reoccupied by local peoples who survived, though he does not rule out occupation by immigrants, likely from Honduras. Or it could be both.
Whoever lay behind the construction, we can wonder why they would invest as much as they did.
Ichikawa proposes they used the volcanic rock not only for functionality but for religious purposes. In Mesoamerica volcanoes were held sacred, he points out.
He doesn’t embrace the theory of a centrally-controlled government underlying the construction, though powerful local leaders may well have done: “I believe that survivors and/or re-settlers in the Zapotitán Valley may have constructed the monumental public building at San Andrés in response to the massive TBJ [Tierra Blanca Joven] eruption,” he writes. And then again after the Loma eruption.
And then, in the post-eruption period from about 600 to 900 C.E., which was the "classic period" in history of the Mayans, San Andres would become what Ichikawa calls a primary regional center. The Classic period was a time of monumental Mayan construction. And maybe, Ichikawa suggests, San Andres with its volcanic-rock pyramid became the focal point for the folk memory of catastrophic eruptions.