| Park Map
Pueblo Bonito beneath
the Cretaceous Cliffhouse Sandstone
is the largest of 14 pueblo great houses built by the Anasazi
in Chaco Canyon between 900 and 1150 CE. The D-shaped floor plan included several stories,
800 rooms, and a central plaza with 32 ceremonial kivas. Archeologists
and anthropologists agree that Chaco was the focus of Anasazi
life in the San Juan Basin, although the nature of the relationship
is debated. The influence is inferred from architectural and
pottery similarities and a network of ancient roads to outliers
like Salmon Ruin and Aztec Ruins near Farmington, New Mexico.
At first glance,
the area around Chaco Canyon seems fairly desolate, not at all
the sort of place you'd expect a community of 5000 to live and
thrive. But the climate was a little wetter 1000 years ago and
the canyon receives storm runoff from a significant area. With
creative planning and labor intensive irrigation techniques there
was enough food to support a growing population.
Why Did They
A 50-year drought
began in 1130 and coincided with a downward turn in Chaco activities.
What would you do if food started getting scarce? As your stores
were depleted you'd have to work harder to bring in crops under
drought conditions. You'd stop building new houses and may not
worry as much about where you threw your trash (both of which
happened). As the drought continued you'd start to wonder if
you'd be better off leaving and finding a better home. Finally,
you would pack up your family and essentials and move on. There
is no evidence at Chaco of violence or sudden abandonment. People
just bit by bit packed up and left. By 1300 Chaco was deserted.
Bonito was first excavated between 1896 and 1899. This photograph
was taken by George H. Pepper from the north mesa overlooking
the great house. Chaco Wash is the dark line between the ruins
and the far mesa.
1941, part of the canyon wall we're standing on broke away from
the mesa to the left of this photo. A section of the ruin rear
wall and some rooms were destroyed.
view has been widened to the left to show the entire ruin and
the 1941 rockfall.
Tree rings are useful for
more than dating. They
can also help identify timber source areas, a method called tree-ring
sourcing. Recent work indicates that most wood came from the
Zuni Mountains before 1020 CE and the Chuska Mountains afterwars.
So how did Chaco builders drag 5-m beams 75 km without pack animals
and and hardly scratch the wood. And once there, how did they
lift the heavy beams up to a six-story height?
Diamond, Jared (2016), Archaeology: Sources of Chaco wood. Nature
529, 31-33. http://dx.doi.org/10.1038/nature16864
Guiterman, C. H., Swetnam, T.
W. & Dean, J. S. (2015), Eleventh-century shift in timber procurement
areas for the great houses of Chaco Canyon. Proc. Natl
Acad. Sci. http://dx.doi.org/10.1073/pnas.1514272112