During my visit to Peru, the most amazing thing I saw were the ancient Inca stone structures present in areas such as Cusco, the Sacred Valley, and of course at Machu Picchu. In these areas the original structures are still standing today, hundreds of years after their construction. This is a tremendous testament to the skills of the Inca engineers since Peru regularly experiences strong earthquakes that score over 7.0 on the Richter scale. In these earthquakes modern buildings are completely destroyed while the Incan structures remain standing.
To build walls, the Incas used a mortarless construction with irregularly shaped rocks that were placed together much like a jigsaw puzzle. In addition to shaping the rocks to fit together on the wall face, they also carved or grinded the rock surfaces that met to have concave and convex surfaces.
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This type of construction is very resistant to earthquakes: The lack of mortar allows rocks to move independently during an earthquake and since the rocks were irregularly shaped they would fall back into their proper place as the earthquake subsided.
In constrast to the Inca stonework, the Spanish used a brick and mortar construction. This had the advantage of being much easier and quicker to build, but would fall apart with any major earthquake. For example, in Cusco the Spanish church built on top of Qoricancha was destroyed by an earthquake in 1950. The Incan foundation remained untouched.
Although we can study the completed Incan structures, the method by which they built them is unknown. The Incans had no written language and any knowledge that would have been passed on to their descendents with an oral tradition was lost after the Spanish conquest. Today, researchers can only guess at the techniques they used and there are no definitive answers to questions such as:
- How did the Incas move stone blocks from the quarry to their construction site? At Sacsayhuaman, many of the blocks are huge and weigh over 100 tons. At Ollantaytambo, the quarry was several kilometers away on the other side of the valley.
- How were the stones cut and shaped so that they would fit together perfectly? In the best stonework, the gap is so small that it would be hard to slide a sheet of paper between the stones.
- How were the blocks lifted and placed into position? The Incan’s did not have access to pulleys and the blocks could weigh many tons.
The best part of this is that the Spanish church fell down while the Incan foundation remained intact. So much for “advanced” civilization. Great article!
Great article
The stones were moved with water. There is a spring at Machu Picchu . All one would need to do is to fill a cistern with water. Connect that cistern to ropes that ran around a simple roller and then down to the stones to be lifted from the river. Fill the cistern until it’s weight was slightly greater than the weight of the stone to be lifted and then the stone will rise to the height of Machu Picchu. Or perhaps they just had some people load themselves into the cistern and ride down, but that was likely done only at the end of the day as they would have to climb back up. At the height of Machu Picchu they either pumped water into a cistern that was held at a height higher than that of the construction or else they had people load into the cistern weight. People are mostly water anyway. As for how they ground the stones to fit so tightly they just used the cistern counterweight to hold the stone where it was to go and just slid it back and forth to grind the stones together so they would fit perfectly. This method would work and it is probably how it was done. There was a video on the net about people trying to recreate how the stones of Ankor Wat, or some other area of ancient construction were fitted together so precisely and they tried the method of wetting them and rubbing them together, it worked perfectly.
The stones were moved from the quarry to the river by attaching floats to them. Stones already displace some of their weight in the water, which is why it is easier to lift heavy stones under water than on dry land.Even a stone that has sunk to the bottom of a body of water is still “floating”. The amount of additional water to be displaced to make a stone rise to the surface is less than the amount of water to be displaced to lift them out of the water completely. This is known as the Archimedes Principle if I remember correctly. Lifting a stone out of the water and putting it on a boat is not practical as the boat needs to displace more water and it is much more unstable and prone to capsizing as the center of gravity is above the water. This is why it is dangerous to stand up in a canoe or small boat, you raise the center of gravity. So the practical thing to do is to tie the stone to the bottom of a boat, one of their reed boats is ideal for this purpose, or attach inflated bladders to the stone so it bobs near the surface of the water. The process would be that they would quarry a bunch of stones and then flood the quarry. They would then float the stones with boats or bladders and move them through a canal or channel to the river. From there they would transport them to the site for lifting by a cistern counterweight.
An alternate method of raising the stones to the height of Machu Picchu would be to have a series of locks going up the side of the mountain. In some show I watched a few years back they mentioned that there was evidence that they had some terraces going all the way down the mountain for growing crops.It would not have been difficult for them to build a series of locks that zig zagged up the mountain. In that case they could just have left the blocks on their floats and moved them up this way. St the top they could have built mud walls around the structure to be built and flooded the area, raising the water level for each new course of stone.