How Machu Picchu’s builders cracked it

A geologist claims to have solved the mystery of the construction of Machu Picchu.

A geologist claims fault lines gave builders the right material to create Machu Picchu in the Peruvian Andes.

Its spectacular location in the Peruvian Andes has made Machu Picchu a magnet for trekkers and selfie-seekers but puzzled generations of archaeologists.

Now a geologist claims to have solved the mystery, saying the ­ruined city owes its position atop a narrow ridge at 2430m to a series of fault lines that created its building materials.

Machu Picchu was constructed in the 1400s only 74km from the historical Inca capital of Cusco yet so remote that it was not discovered by the conquistadors. The site, which may have been a ­sacred centre, a royal citadel or both, has buildings with mortar-free masonry so fine that it is impossible to slide a credit card between the huge stone blocks.

Rualdo Menegat, of the Federal University of Rio Grande do Sul in Brazil, said it was the specific nat­ure of the site that made this possible, with the collision of tectonic plates fracturing the rock to create loose blocks ideally shaped for construction. He said: “Machu Picchu’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 … the intense fracturing there predisposed the rocks to breaking along these same planes of weakness, which greatly reduced the energy needed to carve them.”

Using satellite imagery and field measurements, the geologist mapped a web of intersecting fractures and faults beneath the ­UNESCO world heritage site.

Because some of the faults are oriented northeast-southwest and others trend northwest-southeast, they cross beneath Machu Picchu to form an X. Mapping suggests that structures on the site are oriented along the faults, where suitable stone would have been most abundant. The faults also helped to drain Machu Picchu during rainstorms, which may account for its remarkable preservation, Professor Menegat said.

The Times