Chaco Canyon Β· Archaeoastronomy Β· forge3d Β· USGS Lidar Β· Leaflet
βοΈ SOLSTICE
The sky over Chaco Canyon, computed against the real skyline. At Chaco the horizon isn't flat: the canyon walls are the horizon. SOLSTICE traces each great house's own skyline from USGS lidar and puts every sunrise of the year on it, so you can watch the Sun walk along the rim toward June and back. It shows the live Sun and Moon, whether Pueblo Bonito is in sunlight yet, the Sun Dagger on Fajada Butte, and where we are in the Moon's 18.6-year standstill cycle.
The hero is a forge3d flight down the canyon at summer solstice sunrise, from Fajada Butte past Una Vida, Chetro Ketl and Pueblo Bonito to PeΓ±asco Blanco: 5-metre lidar terrain, NAIP aerial photography, and the Sun where it really is. It renders on GitHub's CPUs with a software Vulkan driver, no graphics card needed. Rebuilt in October 2026 with verified site locations and corrected sky claims.
| Site | Rooms | Period | Notable |
|---|---|---|---|
| Pueblo Bonito | ~800 | 850β1150 CE | Largest great house in the canyon. Its long south wall runs almost exactly eastβwest. |
| Chetro Ketl | ~500 | 1010β1110 CE | Unique colonnade. 4 stories. One of the finest examples of Chacoan masonry. |
| Casa Rinconada | β | 1000β1100 CE | Great kiva. Solstice light through a northeast window is a famous but debated claim: that wall was rebuilt after the 1930s excavation. |
| Pueblo del Arroyo | ~280 | 1075β1115 CE | Adjoins rare tri-walled structure. Late occupation. |
| Hungo Pavi | ~150 | 900β1100 CE | Largely unexcavated. Its plan is well preserved under the rubble. |
| Una Vida | ~160 | 850β1000 CE | One of the earliest great houses, tucked under the canyon wall. Petroglyphs on the cliff behind it. |
| PeΓ±asco Blanco | ~150 | 900β1125 CE | At the canyon's west end. Below it is the painted panel (hand, crescent, star) often linked to the 1054 CE supernova. |
| Pueblo Alto | ~90 | 1020β1100 CE | On the mesa top, where the Great North Road begins its run of about 50 km to Kutz Canyon. |
| Kin Kletso | ~55 | 1125β1150 CE | Late McElmo-tradition construction. One of the last great houses built. |
| Wijiji | ~90 | 1100β1150 CE | Easternmost great house. Accessible only by foot trail. |
The Alignment at Fajada Butte
High on Fajada Butte, three stone slabs lean against the cliff in front of two spiral petroglyphs. Near midday, daggers of sunlight slip between them and mark the spirals at the solstices and equinoxes. Artist Anna Sofaer found it in June 1977, and later work by Sofaer and colleagues argued the spirals also record the Moon's 18.6-year standstill cycle in shadow.
The Great North Road leaves Pueblo Alto and runs about 50 km toward Kutz Canyon. It is wider and straighter than walking needed, which is why many think it meant something more than travel, though careful measurement shows it isn't a perfect true-north line.
Project Kiva: what the laser sees
SOLSTICE's companion project. Project Kiva is an atlas of twelve archaeological places in bare-earth lidar, from Pueblo Bonito, Aztec, Mesa Verde's Far View and Chimney Rock to Cahokia, Serpent Mound, Newark, Poverty Point and two Wisconsin effigy mounds. Points stream straight out of the USGS 3DEP archive; only the returns that reached the ground are kept. Read the story.
Five relief views (local relief, sky-view factor, openness, a sixteen-sun hillshade and a VAT-style composite) strip away the big landforms so the walls, mounds and ditches show. Drag a line across the aerial photo to see the ground underneath, or turn each site in 3D, rendered with forge3d.
