MEXICO.- In a recent study from the National Autonomous University of Mexico (UNAM in Spanish), lead by physicist Dr. Arturo Menchaca, discovered the soil beneath the south side of Mexico's largest pyramid to be severely dry, putting that side at risk of collapse, like a sandcastle lacking enough water.

Originally, Menchaca and colleagues of his set out to find and record a series a secret underground tunnels in the Pyramid, similar to those found under the neighboring Pyramid of the Moon, by using a muon detector. Muons of sub-atomic particles that pass through most materials, but are sometimes deflected by more dense objects. This way, they can detect if there is less dense air, less dense earth, caves, etc., underground. They could even create a 3D image of the underground passageways that they thought existed under the pyramid.

But, what they found was shocking.

"Our scans show that the pyramid is dryer on one side than in the other; the dry part is very large", with about 10 percent of its volume exceedingly dry due to an excessive exposure to the Sun's rays. The pyramid has actually not been expose that long to the Sun, despite its name. It was only in 1910 that the pyramid was restored and made to look as it is now, exposing it to the sun after centuries of being kept moist under a layer of soil, vegetation and rock.

Menchaca used the sandcastle analogy to describe what is happening to the pyramid, saying its basically been left abandoned to the sun, much like how a sandcastle collapses if not kept moist. Most of Mesoamerica's structures are built from rock and earth.

But, not every archaeologist agree with Dr. Menchaca's theory, at least on how to prevent a collapse. Alejandro Sarabia, director of the Teotihuacan site where the Pyramids of the Sun and Moon are located, humidifying the are could worsen the problem, since the pyramid has been modified in order to preserve it and is no longer just a base made out of earth and stone. Cement has been added in recent decades, for example:

"Several decades ago [in the 1970s], cement was added to between the rock. This gave [the pyramid] stability, and also hindered vegetation growth. But on the other hand, it prevented humidity from evaporating, created by water leaking from cracks." Meaning that the pyramid's real problem might be an excess of water, not lack thereof. UNESCO has actually cited the cement and other previous restoration attempts (together with the construction of a Walmart near the site) as a threat to its status as a world heritage site.

The report says that they are currently considering possible solutions for preventing a collapse or damage to this important heritage site. Although they still have only analyzed 60 percent of the data collected by the scan, with 40 percent remaining and projected to be fully considered by the end of the year.

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Elizabeth.rosales@sandiegored.com

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