Treading lightly in Oak Tree House By By DAVE BUCHANAN The Daily Sentinel

This particular ranger-led tour is a 90-minute out-and-back trip to Oak Tree House, which had been excavated from 1915 to 1921 by Jesse Fewkes for the Smithsonian Institute after earlier excavating Spruce Tree House in 1908 and Cliff Palace in 1909. Oak Tree House, named for a massive oak tree which since has fallen, has been closed to the public since the early 1930s.

This summer, ranger-led hikes to Oak Tree House and Mug House, which the park never has opened to public tours, will be offered on an advance registration-only basis….

Oak Tree House, like nearly all of the 600 or so known cliff dwellings in the park, is found in a shallow cave eroded by groundwater percolating through a massive layer of Cliffhouse Sandstone. It’s the topmost layer of the Mesa Verde group of shoreline sediments laid down more than 65 million years ago. …

Why did people ignore these caves for most of their occupation of Mesa Verde? Of the more than 4,500 dwellings identified in the park, only 600 or so are cliff dwellings, and their occupancy dates only from the last century the people lived here.

No one knows for sure, but some educated guesses suppose that at its peak, the local population reached nearly 3,000 and there was a growing demand to find new places to live, new resources to exploit, or perhaps new enemies to avoid.

An even bigger question is, why did they leave?

The Great Drought of 1276-1299 certainly had some impact. Perhaps overpopulation, caused in part by better nutrition as farming techniques improved, had a part, or even disease resulting from living in close quarters with tamed turkeys and dogs.

Around 1300, the residents suddenly abandoned these elaborate cliff dwellings and migrated south to the Rio Grande Valley of New Mexico and to one region of northern Arizona.

Today, 24 American Indian tribes claim some connection to the people who lived in Mesa Verde.

When the environment could no longer sustain the Ancestral Puebloans, it forced total emigration, said Jim Judge, professor emeritus at Fort Lewis College in Durango.