Machu Picchu: 15th Century Incan Sanctuary Purposely Built on Faults

     "The ancient Incan sanctuary of Machu Picchu constructed in the mid to late 15th century, is considered one of humanity's greatest architectural achievements. Built in a remote Andean setting atop a narrow ridge high above a precipitous river canyon, the site is renowned for its perfect integration with the spectacular landscape. Yet the sanctuary's location has long puzzled scientists -- Why did the Incas build their masterpiece in such an inaccessible place? Research suggests the answer may be related to the geological faults that lie beneath the site."(Wow, ancient ecoarchitects meet ancient Scientific Stephs ;-)).

          

       "On September 23, 2019, at the Geological Society of America (GSA) Annual meeting Dr. Rualdo Menegat, a geologist at Brazil's Federal University of Rio Grande do Sul,  presented the results of a detailed geoarchaeological analysis that suggests 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," says Dr. Menegat. "It would be impossible to build such a site in the high mountains if the substrate was not fractured."

    " Using a combination of satellite imagery and field measurements, Menegat mapped a dense web of intersecting fractures and faults beneath the UNESCO World Heritage Site. His analysis indicates these features vary widely in scale, from tiny fractures visible in individual stones to major, 175-kilometer-long lineaments that control the orientation of some of the region's river valleys."

     "Dr. 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. X marks the Machu Picchu spot.

     "Dr. 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," says Dr. Menegat. Other ancient Incan cities, including Ollantaytambo, Pisac, and Cusco, are also located at the intersection of faults, says Menegat. "Each is precisely the expression of the main directions of the site's geological faults."

     Dr. Menegat's results indicate the underlying fault-and-fracture network is as integral to Machu Picchu's construction as its legendary stonework (as above). This mortar-free masonry features stones so perfectly fitted together that it's impossible to slide a credit card between them. Aside from the obvious aesthetic benefits of this building style, there are engineering advantages. Peru is a seismically unstable country; both Lima and Cusco have been leveled by earthquakes. When an earthquake occurs, the stones in an Inca building are said to “dance;” that is, they bounce through the tremors and then fall back into place. Without this building method, many of the best known buildings at Machu Picchu would have collapsed long ago.

       "As master stoneworkers, the Incas took advantage of the abundant building materials in the fault zone, says Dr. Menegat. "The intense fracturing there predisposed the rocks to breaking along these same planes of weakness, which greatly reduced the energy needed to carve them."

     "In addition to helping shape individual stones, the fault network at Machu Picchu likely offered the Incas other advantages, according to Dr. Menegat. Chief among these was a ready source of water. "The area's tectonic faults channeled meltwater and rainwater straight to the site," he says. 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, Dr. Menegat explains."

     "The faults and fractures underlying Machu Picchu also helped drain the site during the intense rainstorms prevalent in the region. "About two-thirds of the effort to build the sanctuary involved constructing subsurface drainages," says Dr. Menegat. "The preexisting fractures aided this process and help account for its remarkable preservation," he says. "Machu Picchu clearly shows us that the Incan civilization was an built on well-fractured rocks. 

Have any PEOTS folks visited Machu Picchu? How was the experience?

And Happy 6 year anniversary to PEOTS! 

• We had a Japanese cardiologist stay with us in March 2008. He took the leftover Colorado trail GORP with him to his next stop at MP and sent this image. So it's almost like I've been there...and it looks deserted.

Who Nose? -- Nothing to Sniff at: Mammalian Brains and Distinguishing Odors

     "Neuroscientists have discovered that at least six types of mammals -- from mice to cats -- distinguish odors in roughly the same way, using circuitry in the brain that's evolutionarily preserved across species.

       The world is filled with millions distinct smells, but how mammals' brains evolved to tell them apart has been something of a mystery.

       Now, in a study published today, two neuroscientists from the Salk Institute and UC -- San Diego have discovered that at least six types of mammals distinguish odors in roughly the same way, using circuitry in the brain that's evolutionarily preserved across species.

      "The study yields insights into organizational principles underpinning brain circuitry for olfaction in mammals that may be applied to other parts of the brain and other species," says Dr. Charles Stevens, distinguished professor emeritus in the Salk Lab.

     In brief, the study reveals that the size of each of the three components of the neural network for olfaction scales about the same for each species, starting with receptors in the nose that transmit signals to a cluster of neurons in the front of the brain called the olfactory bulb which, in turn, relays the signals to a "higher functioning" region for odor identification called the piriform cortex.

     "These three stages scale with each other, with the relationship of the number of neurons in each stage the same across species," says Dr. Shyam Srinivasan, assistant project scientist with UC San Diego's Kavli Institute for Brain and Mind, and the paper's coauthor. "So, if you told me the number of neurons in the nose, I could predict the number in the piriform cortex or the bulb."

      The current study extends research by the same authors, published last year in which described how mouse brains process and distinguish odors using what's known as "distributed circuits." Unlike the visual system, for example, where information is transmitted in an orderly manner to specific parts of the visual cortex, the researchers discovered that the olfactory system in mice relies on a combination of connections distributed across the piriform cortex.

     Following that paper, the authors sought to determine if the distributed neural circuitry revealed in mice is similar in other mammals. For the current work, the researchers analyzed mammal brains of varying sizes and types. Their calculations, plus previous studies over the past few years, were used to estimate brain volumes. 

      The new study revealed that the average number of synapses connecting each functional unit of the olfactory bulb to neurons in the piriform cortex is invariant across species.

      "It was remarkable to see how these were conserved," says Dr. Stevens.

     Specifically, identification of individual odors is linked to the strength and combination of firing neurons in the circuit that can be likened to music from a piano whose notes spring from the depression of multiple keys to create chords, or the arrangement of letters that form the words on a page.

       "The discrimination of odors is based on the firing rate, the electric pulse that travels down the neuron's axon," says Srinivasan. "One odor, say for coffee, may elicit a slow response in a neuron while the same neuron may respond to chocolate at a faster rate."

      This code used for olfaction is different than other parts of the brain.

     "We showed that the connectivity parameters and the relationship between different stages of the olfactory circuit are conserved across mammals, suggesting that evolution has used the same design for the circuit across species, but just changed the size to fit the animals' environmental niche," says Dr. Stevens.

     In the future, Dr. Stevens plans to examine other regions of the brain in search of other distributed circuits whose function is based on similar coding found in this study.

     Dr. Srinivasan says he will focus on how noise or variability in odor coding determines the balance between discrimination and learning, explaining that the variability the duo is finding in their work might be a mechanism for distinguishing odors, which could be applied to making better machine learning or AI systems."

     Smell-o-vision, anyone?

Stay cool and not stinky,
Steph

April Arkansas Gems, Fossils, and Meanderings

       A post about Arkansas gems, fossils, and rocks is overdue. This crinoid piece is especially well-preserved. Here is a bit more information about crinoids.

     We spent many hours sorting and breaking apart Mississippian and Ordovician rocks. What joy!

Quartz crystals: 

Crinoid stalk or stem pieces:

     This sample was not available to bring home :-(.

But, this brachiopod sample  was: 

       My Mom, Smith College friend, Karen, and I had a great time exploring northwest Arkansas.We found brachiopods, crinoids, quartz crystals, and explored Crystal Bridges Art Museum, Thorncrown Chapel, the Ozark Folk Center and Blanchard Springs Caverns located in Fifty-Six, AR. Little Rock Central High School was the last stop before dropping Karen at her aunt's home in Hot Springs and heading back to Bentonville.

     We almost missed the road to Thorncrown Chapel, even though we were expressly looking for it. It was worth the trek!

        The outdoor artwork and plantings are some of my favorite parts of Crystal Bridges.

     Pappy and Lightning entertained us at the Ozark State Park Folklore Center.
   

     More highlights:

      Mom and Maizie were big fans of the Frank Lloyd Wright home:

      We enjoyed the geodesic dome:

       Alas! I left my iPad atop my trusty Subaru at one of the last overlooks on the way from Hot Springs to Bentonville. I saw it fly off in the rear view mirror. The photos were not in the cloud. So, a few photos from my friend and from my phone remain. It was most memorable and mom can now answer the question “Why are you going to Arkansas?” with some of these images. 

      Mom liked the half-mile trek through Blanchard Springs Caverns in Fifty-Six, especially.

        And we all really liked the giant bronze spider, Maman, holding her marble eggs protectively over the main entryway at Crystal Bridges.

        [I am writing this on my phone without a 'u' key so the photos will do most of the talking this time around.]


        Hope you'll have a chance to make Arkansas plans some time. It is The Natural State and it is a Gem!

Steph

What the Sand Hill: Cranes, Lanes, and Automobiles

      Maizie, my field assistant and resident canine, and I enjoyed a two-day trek to observe the Sand Hill Cranes migrating northward in the San Luis Valley in south central Colorado. 

      We started at Great Sand Dunes National Park and Preserve, of course.

      We spent some time listening to the cranes in San Luis State Park, although we did not see many of the graceful birds.

     We wondered what this unidentified two story building 

with a locked gate is adjacent to the Mosca Campground, seen in the left-center part of this image (very mysterious-but, I digress).

      Our next day search for the Sand Hill Cranes took us first to the Alamosa Wildlife Preserve and then, enroute to the Monte Vista Wildlife Preserve, to a cow pasture adjacent to a very narrow two-lane road.

     We were alone with the birds and the cows when this noisy, chortling flyover of Sand Hill Cranes happened. Some have asked if I took the video; no, it was Maizie with her crazy-good iPad filming skills. The video is 3:39 long and gets very exciting a few seconds in. 

       Antigone canadensis (which are classified as part of the Gruidae family) currently number 450,000 or so in North America. They are ancient birds, having origins 2.5-10.5 million years ago, depending on classification.

     Here's hoping you will see or have seen these magnificent creatures, especially as they dangle their legs for a perfect landing.

What the Sand Hill?
Steph