Washington: The Incan sanctuary of Machu Picchu -- considered one of humanity's greatest architectural achievements -- was intentionally built in a location where tectonic faults meet, according to a study. Built in a remote Andean setting atop a narrow ridge high above a precipitous river canyon in Peru, The UNESCO World Heritage Site is renowned for its perfect integration with the spectacular landscape.
However, the 15th-century sanctuary's location has long puzzled scientists who wonder why the Incas built their masterpiece in such an inaccessible place. New study suggests the answer may be related to the geological faults that lie beneath the site.
According to Rualdo Menegat, a geologist at Brazil's Federal University of Rio Grande do Sul, the Incas intentionally built Machu Picchu -- as well as some of their cities -- in locations where tectonic faults meet.
"Machu Pichu's location is not a coincidence. It would be impossible to build such a site in the high mountains if the substrate was not fractured," said Menegat. Using a combination of satellite imagery and field measurements, Menegat mapped a dense web of intersecting fractures and faults beneath the site.
Menegat found that these faults and fractures occur in several sets, some of which correspond to the major fault zones responsible for uplifting the Central Andes Mountains during the past eight million years. Because some of these faults are oriented northeast-southwest and others trend northwest-southeast, they collectively create an "X" shape where they intersect beneath Machu Picchu.
Menegat's mapping suggests that the sanctuary's urban sectors and the surrounding agricultural fields, as well as individual buildings and stairs, are all oriented along the trends of these major faults. "The layout clearly reflects the fracture matrix underlying the site," said Menegat. Other Incan cities, including Ollantaytambo, Pisac, and Cusco, are also located at the intersection of faults, said Menegat.
As master stone-workers, the Incas took advantage of the abundant building materials in the fault zone, said Menegat. "The area's tectonic faults channeled meltwater and rainwater straight to the site," he said.
Construction of the sanctuary in such a high perch also had the benefit of isolating the site from avalanches and landslides, all-too-common hazards in this alpine environment, Menegat said. The faults and fractures underlying Machu Picchu also helped drain the site during the intense rainstorms prevalent in the region.