Above, the Spruce Tree House, the best preserved cliff dwelling in the park, was closed to the public in 2015 after a rock fall and subsequent investigation.
Mesa Verde, which means green table in Spanish, is a high (elevation of 8,100 feet/2,470 m) table of sandstone, cut by canyons. The mesa is tilted 2-3 degrees to the south, helping crops and people to get more sunlight and warmth, important at this altitude. The sandstone is a soft stone, enabling the canyons to be cut without a large watershed.
The people who first settled here are now known as Ancestral Puebloans. From around AD 550, they farmed on the mesa and built pithouses, a sunken house of poles and mud.
Structures progressed to houses of poles and mud above ground, then to stone masonry. These houses were on the mesa top and on cliffs. “About A.D. 1200, another major population shift saw people begin to move back into the cliff alcoves that sheltered their ancestors centuries before.”
Ancestral Puebloans lived in the cliff dwellings for less than 100 years. By about A.D. 1300, Mesa Verde was deserted. Several theories offer reasons for their migration. We know that the last quarter of the A.D. 1200s saw drought and crop failures—but these people had survived earlier droughts. Maybe after hundreds of years of intensive use the land and its resources—soils, forests, and animals—were depleted. Perhaps there were social and political problems, and the people simply looked for new opportunities elsewhere.
From page 135 of The West Without Water, tree ring data “reveal that the droughts from AD 1276 to 1299 were tied to failures of the summer monsoon rains.” Researchers from the US Geological Survey found that “major human migrations occurred during prolonged periods of drought, particularly when the summer monsoon rains failed.” “Most likely, a good harvest would have yielded enough food for the current year, plus one year’s reserve, but no more. Multiyear failed harvests would have been devastating to the growing population.”
Mesa Verde is a UNESCO World Heritage Site.