| The Chaco Meridian In February of 1990, I noticed that Big Horn Medicine Wheel, Aztec Pueblo, the Pueblos of Chaco Canyon, and the Mimbres Valley are all situated on an approximate north-south line near the 108th meridian. This observation was an outgrowth of my rock art fieldwork and, previous to that, an interest in ancient astronomy as evidenced in architecture. I had first noticed a group of rock art sites with similar images on an approximate meridian. Thereafter I began studying maps of and mapping unmapped archaeological sites. In 1991 I noticed that Casas Grandes, in Northern Mexico, was on the same meridional concentration. Meridians have been used historically to determine the scale of the earth, so I gave these near-meridional sites further attention and noticed that Mt. Wilson, one of the highest peaks in the Rockies, was on this meridian. At that time I named the alignment the "Chaco Meridian." I later noticed that the arc distance from Pueblo Bonito to Mount Wilson precisely equals 1/200th of the circumference of the earth, or 1.80 modern degrees. Likewise, of course, for the latitude difference from Mt. Wilson to Pueblo Bonito and Chetro Ketl. NEW - Ancient Monuments Placemarks | Southwest Archaeology Placemarks
After observation of the meridional alignment of these American Southwest sites, I examined other areas for other arrangements. In February of 1991 I first noticed a meridional concentration for the Dzibilchaltun observatory, Merida (prehistoric Tiho), Sayil, Kihoic, Hormiguero, Uaxactun, Tikal, Las Tinajas, and El Trapiche (Tazumal). I termed this alignment the "Maya Meridian." On March 21, while checking the distances between Chac Mools, I noticed the 1/36 of circumference distance (10.0 degrees) from the Tenochtitlan pyramid to the Castillo pyramid at Chichen Itza (both have Chac Mools in their interiors). I also noticed the Tikal to Chichen Itza arc distance of 1/100 of circumference. During Nov. 1991, to accurately check site-to-site relationships at greater distances, I began using spherical trigonometry. I discovered that the Newgrange-Cheops arc equals 1/10th of circumference and the Newgrange-Avebury arc equals 1/100th of circumference. These early findings prompted continued inquiries, and more site relationships have since been noted. Some evidence infers a relationship between the Chaco Meridian and the Maya Meridian. A more detailed explanation of my concepts regarding the relationship of ancient monuments to geodesy and geodesy-related astronomy is found in the Archaeogeodesy article series.
At Pueblo Bonito, the north-south alignment of the central wall and the east-west alignment of half of the south side are well known. In academic publications, the Chaco phenomena has been a focus of careful astronomic study since publication of "A Unique Solar Marking Construct" by Anna Sofaer, Volker Zinser, and Rolf M. Sinclair (Science, 19 October 1979, Volume 206, Number 4416, pp. 283-291). Sofaer, et.al.'s Fajada Butte study demonstrated complex astronomy for both Chaco Canyon and southwest rock art placement and epigraphy. The Fajada Butte archaeoastronomy discovery focused my attention on southwest rock art and on these authors for one of the first times. Fajada Butte is an illumination hierophany on a small scale relative to Great House lines and alignments the authors later considered. Again in 1982 and 1983, Sofaer and others published on "astronomical markings" and "lunar markings" on Fajada Butte. Sofaer, Michael P. Marshall, and Rolf M. Sinclair noted the relative longitudinal positions of major sites in their 1989 publication "The Great North Road: a Cosmographic Expression of the Chaco Culture of New Mexico" in World Archaeoastronomy, edited by A. F. Aveni, New York: Cambridge University Press.
Chaco Canyon and the broader Chacoan sites present a rich array of massive architectural constructs in a context of an extensive, straight-line road complex, fertile ground for continuing study and more refined focus. In 1997 Sofaer, writing "The Primary Architecture of the Chacoan Culture: A cosmological expression," postulates the role of Puebloan astronomy in the placement of Chaco Canyon Great Houses and the arrangement of outlying pueblos. Her extensive references provide a useful long list of important previous studies on Chaco and archaeoastronomy in addition to the academic context of her findings. In 1999, Robert Redford narrated and Sofaer directed The Mystery of Chaco Canyon.
Archaeologist Stephen Lekson, presumedly unaware of my unpublished geodesy studies (I made several private communications to other archaeologists), published a book entitled "The Chaco Meridian" in 1999, focusing popular attention on the longitude coincidence of the centers of political power, Aztec, Salmon, Chaco, and Casas Grandes. (Read a critical discussion of Stephen Lekson's book.) One of the criticisms directed at Lekson's political concept is the inaccuracy of the longitudinal alignments. Precision of coincidence on a north-south line is only one consideration in relation to possible ancient geodesy. Meridians are a fundamental geodetic and astronomic tool, but use of a meridian does not require aligning pueblos with precision on a simple North-South line. The width of the Chaco Meridian, the overall difference in longitude between Casas Grandes and Aztec is about 0.05 degrees (see figure following). The longitude equals less than a three mile baseline at Casas Grandes. The Pueblo del Arroya and Chetro Ketl great kivas are situated at 0.00983 arc degrees, near East-West 1,093 m apart. Note, also illustrated below, the number of Chaco Canyon Great Houses between the Mt. Wilson (mtwi) and Casas Grandes (cags) longitudes. Sofaer hypothesized, for inter-visible Great House arrangements at Chaco Canyon, major wall and site-to-site astronomical alignments. Rather than a simple meridian, a similar level of complexity can be expected in any intentional site arrangement beyond the range of intervisibilty.
The arc distance from Mt. Wilson to Pueblo Bonito and to Chetro Ketl is near 200 km, 1/200th earth's circumference (cir/200), as are their respective latitude differences. In addition to 14,246 foot Mt. Wilson, two other 14,000 foot peaks crown the Rockies north of Chaco, Uncompadre Mountain, the tallest at 14,308 and Mt. Eolus at 14,084, along with Hesperus Mountain at 13,232 ft. The latitude difference between Uncompadre and Mt. Eolus is 0.4498°, cir/800. The latitude and longitude differences between Uncompadre and Hesperus mountains are equal. Pueblo Bonito is 1/2 degree west of Uncompadre, and 0.1271° east of and 1.3845° (cir/260) south of Hesperus.
Including relationships to major peaks in site arrangement considerations adds to the complexity of assessing the meridional sites concentration. Site arrangements on an even larger scale, extending beyond the Chaco Culture region, is another complicating factor. A first step in defining the relationships of the constructions is accurate knowledge of their placements. Recent high resolution image updates in Google Earth™ adds to previous resources. However, GPS readings of major kivas, walls, corners, etc., are required to accurately reconsider preliminary results based on map-derived coordinates. In the Spring of 2007, I completed a GPS survey of the major architectural features mentioned herein, and will add new information after further study using the new data. Some GPS-determined coordinates follow.
2008.04.16 - After a year, I've taken time to publish 2007 GPS survey data. All waypoints and current derived coordinates are in a Southwest Waypoints spreadsheet (sw_waypoints.xls). A first version of the placemarks file is now uploaded (southwest_archaeology.kml). The placemarks illustrate a difference between current Google Earth coordinates in this area and the WGS84 coordinate system. Accuracy on the digital globe varies by region, and coordinates can change as updates improve imagery placement.
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