Case Study: Inca Stonework
As mentioned in the previous post, the Inca were renowned for their amazing and unique stonework. Since their use of stone made it difficult to change plans or go back and fix something later on, the Inca could not mess up during construction and had to make sure everything was well-planned. They were inspired and expanded on Pre-Inca influences, including the Wari and other Peruvian/Bolivian earlier groups. One trademark of Inca architecture was how the Inca blended the artificial and natural, incorporating natural outcrops into stairs, walls, and even thrones. Their use of the natural landscape turned their sites into intricate lived-in landscapes, in which natural and human forces become entangled. In Machu Picchu, the Inca built the site around the landscape: using it to enhance the site's beauty and functionality. The Inca so much valued the natural landscape around it, that Machu Picchu was built as a way to mirror these features. See the image below for one example.
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| Intihuatana stone - https://www.annees-de-pelerinage.com/machu-picchu-architecture-explained/ |
Engineering: Machu Picchu
In an article for American Scientist, engineer Henry Petroski presents his studies of the Inca's stonework and engineering used to build Machu Picchu. Here, I present the highlights of his findings:
The engineering profession recognizes the prowess of the 15th-century Inca" (pg. 15)
Machu Picchu is one of the best preserved Inca sites. Due to its remote location, unlike many other sites, especially in near-by Cusco where many were destroyed by the Spanish, it survived the Spanish invasion. Nearly five hundred years later, four hundred of which were spent unmanaged and overgrown by jungle, Machu Picchu is in remarkable condition. It has survived earthquakes, landslides, and so much more. All of this is due to its extensive engineering by the Inca during construction. Machu Picchu is built of virtually only stone and soil. Because of its limited accessibility and the Inca's lack of large draft animals, it had to be largely self-sustainable, so the Inca sourced stone from quarries very near to the site.
"The Inca were presented with a challenging and interrelated set of problem in planning and engineering that had to be solved in order to ensure that everything worked as conceived ... And it all does work, even after about three-and-a-half centuries of being neglected and another century since it was uncovered from dense jungle overgrowth” (pg. 17)
Underground Construction
It has been argued that more than 50% of Inca construction exists underground, and Machu Picchu is not an exception. Petroski describes how wall foundations of terraces help stabilize the site and even provide foundations for buildings. The site's endurance (especially when faced with earthquakes) can largely be attributed to this underground support.
Image from Cusco 1950 earthquake that left 1/3 of the city destroyed but most Inca structures untouched - http://www.limaeasy.com/earthquakes-in-peru/historical-earthquakes/20th-century-earthquakes
Another feature of underground construction is Machu Picchu's advanced water drainage systems. The best example of water drainage was the terraces built into the side of the site. Drainage was essential to the functionality of the terraces. To ensure everything worked well, the Inca terraces featured four different levels. From top to bottom: top soil, sand and gravel, larger gravel, and finally stone chips from wall construction debris all ensured that water properly filtered down through the terraces. The Inca also built the terraces inclined about 5% backwards and stone backed to ensure stability.
Terrace Diagram - https://ascelibrary.org/doi/10.1061/%28ASCE%29SC.1943-5576.0000146
Water
Water played a vital role above ground as well. Once again the Inca had to plan how to construct a system that supplied enough water for its populations. To do so they first chose a site that was received more rainfall than the surrounding, drier areas. This ensured that their water source, a natural spring on the north side of the mountain, was constantly replenished. The spring could sustain a population in the thousands, the Inca just needed some way to get the water to where it was needed.
The Inca devised a series of fountains and open channels that spread throughout Machu Picchu. The royals were given priority, with water flowing through their residences before it went anywhere else. The channels were carved to flow away from walls, avoiding excess splashing that would have left them susceptible to erosion. The Inca also carved spaces that perfectly fit their "aryballos" or water collecting devices.
Water Fountain - http://www.rutahsa.com/mp-fountains.html
Aryballo - https://www.vcoins.com/en/stores/ancient_artifacts__treasures/4/product/large_inca_aryballos_cusco_style_ca_12501500/7716/Default.aspx
Structures
Of course, Petroski knows that what draws millions of people to Machu Picchu today is generally not an interest in hydraulics, but rather the two-hundred plus stone structures that exist above-ground. This is not without good reason. The Inca built Machu Picchu to be beautiful, contrasting geometric patterns of the terraces with the straight lines of the buildings or the rounded religious structures. The stones are unadorned, but it does not matter because the majesty of the stonework itself commands every bit of awe as those sites that are.
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| https://www.annees-de-pelerinage.com/machu-picchu-architecture-explained/ |
As mentioned in the previous post, the Inca built without mortar, cutting stones into place with one another. This helped increase stability during earthquakes, as the walls would shake around but easily fall back into place once the earthquake ended. Machu Picchu is especially famous for its use of stones cut into a variety of intricate polygonal shapes.
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| Polygonal stones - https://ashtronort.wordpress.com/2016/03/28/precision-fitting-of-massive-incan-blocks/ |
Machu Picchu features many trademark Inca architectural themes. The windows and doors are the traditional trapezoidal shape and proportions (i.e they are pretty short). Some of the stones are flat and finished while others have a unique pillow effect to them, in which they were pounded into a puffy and curved shape. The Inca's attention to detail is also abundantly clear above ground as well. The structures feature circular cylindrical stone projections in which timber and thatched roofs could be balanced. Some stones had holes to hold torches. There are large, grand stairways built out of massive rock or built into or on the natural landscape.
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| Pillow Effect - https://www.ancient-code.com/amazing-examples-of-inca-and-pre-inca-masonry-photos/ |
“On closer view, it is the visible stone-work of the terrace retaining walls and building facades that captures the imagination and brings the site to life.”
One Man's Experience with "Inca Quarrying and Stone Cutting"
An architect, Jean-Pierre Protzen, presents an in-depth investigation into Inca quarrying and stone cutting practices by utilizing both historical archaeological records, ethnography and middle range theory (observing contemporary Peruvian quarries), and experimental archaeology performed by Protzen himself. His research focuses on quarrying, cutting and dressing, and fitting and laying.
Quarrying
When considering quarrying method of the Inca, Protzen specifically wants to learn what stone they used and how they got it. The Inca often chose quarries further away and less accessible, indicating the importance of the type of stone used. Even if inconvenient to manufacture, the Inca valued specific types of stone for specific purposes. Because of the distance, the Inca built well-maintained roads that still exist in some capacity today. The roads featured slides and ramps for accessing different parts of the quarry. Within the quarry, more infrastructure was added, including retaining walls to prevent rockslides, water canals, and possibly on-site residences.
The Inca preferred red or gray granite. To extract granite, in some quarries, workers would use stones already fallen that were well-suited for whatever purpose, not actually removing them the bedrock. These stones were then minimally reworked and sent to the construction site, where fine cutting and shaping took place. In most quarries, however, stone is broken off or extracted. To break the stone was relatively simple, so the Inca could do it using bronze pry-bars or even wooden sticks (as contemporary quarry workers do today). They also may have used wedges of dry wood, but this method is not as certain.
Cutting and Dressing
In Protzen's observance of Inca quarries, he was able to see stones left behind in each part of the manufacturing process from when the Inca actually worked there. He also observed many tools left behind, revealing that the Inca used river cobbles as hammerstones and chisels. He hypothesized that the Inca used the largest stones to square off blocks of stone by flaking methods, and then smaller stones to dress the rocks into finely shaped squares (or other shapes).
To test his conclusions, Protzen himself worked on raw stone with the same tools. He found that the process of repeatedly hitting stone with another rock was actually quite quick and not very energy-consuming. Due to gravity, one could drop the hammerstone, it would bounce back up, and then repeat the process. With the larger stones, the hammerstone did have to be held in a certain way as to not impact the wrist or hand bones. Protzen reinforced that there were also alternative methods used in many different sites to achieve unique and different results.
"The experiments show that stones can be mined, cut, and dressed with simple tools yet with little effort and in a very short time." (pg. 175)
Fitting and Laying
To get a sense for how the Inca so precisely placed their stones on top of one another during construction, Protzen again did his own experiments. He learned that, "through repeated fitting and pounding, one can achieve a fit as close as one wishes" (179). However, he believes the process to be much more laborious and time-consuming than other steps in the process. Although this was not of as much concern to the Inca due to their large labor force, the process of fitting is one of trial and error, testing stones over and over until the fit is just right. Thus, the Inca's proficiency in fitting shows a dedication to the process that manifests itself in the long-lasting beauty of the structures they made.
In terms of laying, the Inca often used a technique called a rising joint, in which stone is well-fitted on the exterior, with gaps in the middle filled in using rubble. The Inca usually used lateral laying sequences, going all the way across before going up. They also frequently placed keystones in their constructions.
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| Sequencing - from Protzen article |
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| Rising Joints - from Protzen article |
Why Does Stonework Matter?
(Thanks for asking, I did not write that much about rocks for nothing.)
Between this post and my first, my goal was to convey the impact of the Inca on the landscape around them. Although the Inca are often disregarded simply because they chose not to write, more and more scientists (not just archaeologists) are beginning to acknowledge and study in-depth the extensive knowledge of the Inca. These were truly a resourceful and creative people: who worked with the environment or shaped it to their needs. They found ways to protect their sites from being destroyed by natural events while also incorporating and praising the natural in them.
However, as I mentioned in the first post, this is not just about the impressiveness of the Inca (although they were very impressive). These facts and this case study are meant to show a contrast. Today, these structures that have survived hundreds of years of natural forces are now being destroyed at an alarming rate by humans. Once again, I mention the fact that in the past ten years, Machu Picchu has incurred more damage than the four hundred it was abandoned beforehand. Vibrations from the thousands of people visiting a day loosens walls in a way that not even earthquakes are capable of. Parts of the site are roped off and even guarded to prevent climbing. People carve their initials into walls or chip pieces off as souvenirs to take home. Its not just the cultural that's threatened though, Machu Picchu is also a diverse ecosystem that is now endangered. Locals report a decrease in trees as they are used for firewood or construction. The Inca trail and Aguas Calientes, the town that one must go through to get to Machu Picchu, are being overtaken by trash and debris. The trail is especially at risk: too many people and not enough amenities mean backpackers are unprepared and leave garbage wherever, start fires in unsafe areas, make anything their bathrooms (even ruins!), and make shelters in inappropriate places (again, the ruins). Even those that are "environmentally conscious" are a problem because there are simply too many of them. Species that live in the area, most especially the rare Andean Spectacled Bear are also threatened. (Meisch, 1985)
One example of action taken to balance tourism with the protection of the environment in Machu Picchu is the Machu Picchu Sanctuary Project, which considers the archaeological sites as part of the environment. Its ironic: things that are human, although they must be very old, are now being considered natural because just like the environment, they must be protected from the actions of modern humans.
So what's the solution? Peru relies on tourism, and rather than limiting or decreasing it, many are looking to expand the industry. Archaeologists, conservationists, environmentalists, politicians, tourists, native Peruvians, and so many more all have their own thoughts and solutions to the Machu Picchu problem, but that's for another post.
Sources
Meisch, Lynn A. "Machu Picchu: Conserving an Inca Treasure." Archaeology 38.6
(November/December 1985): 18-25. Accessed October 11, 2018.
https://www.jstor.org/stable/41730268.
Petroski, Henry. "Engineering: Machu Picchu." American Scientist 97.1 (January/February
2009): 15-19. Accessed October 11, 2018. https://www.jstor.org/stable/27859260.
Protzen, Jean-Pierre. "Inca Quarrying and Stonecutting." Journal of the Society of Architectural
Historians 44.2 (May 1985): 161-82. Accessed October 11, 2018.
https://www.jstor.org/stable/990027.
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