Here, a quarter of a million people per year embark on self-guided tours, scrambling up and down ladders, wiggling through tight doorways and pausing inside kivas. Time seems to slow in this majestic ruin as tourists walk in the footprints of the past.
But Spruce Tree House is crumbling, said Tim Hovezak, preservation archaeology program manager at Mesa Verde, a national park established 110 years ago. The park was designed to protect archaeological sites built by the ancestral Puebloans, but even the best preservation methods are not sustainable.
In short, Hovezak said, the centuries-old structures at Mesa Verde are gradually collapsing. Spruce Tree House, the park’s third-largest cliff dwelling and its most highly visited ruin, is closed to visitorsindefinitely as the National Park Service investigates falling rock.
“Preservation is a delicate balance and it’s something that I don’t think is sustainable,” Hovezak said. “We have tried to keep as many of these sites open as we can, but it’s a question of how long we can continue to do that.”
Mesa Verde National Park, a 52,000-acre wilderness in the southwestern corner of Colorado, boasts nearly 5,000 documented archaeological sites including more than 600 cliff dwellings. The ruins are some of the best preserved in the United States, shedding light on the lives of the ancestral Pueblo people, who made Mesa Verde their home between 600 and 1300 A.D.
Millions of people have visited Spruce Tree House since June 1906 when President Theodore Rooseveltestablished Mesa Verde—Spanish for “green table”—as a way to “preserve the works of man.” But intimate visits to these ruins, nestled deep into alcoves in the sandy cliffs, may be a thing of the past.
“What I think will happen is that we will gradually close more and more of the ruins to the public, or gradually restrict access more and more,” Hovezak said. “Visitors will always be able to view the sites from across the canyons, but they won’t be able to enter them anymore.”
In August 2015, a rock fall at Spruce Tree House prompted park officials to close the ruin temporarily as they completed initial assessments. What they found was decades-old stabilization work crumbling from inside a natural sandstone arch just above the cliff dwelling.
“Pieces of concrete had fallen out of the ceiling,” Hovezak said. “What fell was maybe about a dozen pieces and the total weight was about 10 pounds—enough to hurt someone.”
Park officials dug through historical records and discovered that crews in the 1940s and again in the 1960s had repaired a fracture in the roof of the dwelling, filling it with concrete. Rock layers at Mesa Verde are laid down horizontally, allowing for creation of the alcoves where Pueblos were built, Hovezak said. But horizontal rocks can mean vertical cracks.
“Vertical fractures in these rocks sometimes go from the ceiling of the alcove all the way to the top of the canyon rim,” he said. “Back in the 1960s, the park hired a construction company to drill through the bedrock from a crane on the rim. Miners drilled holes through the bedrock, inserted steel pins to hold the arch in place then filled up the whole crack with concrete.”
Fast forward through 50 years of rain and erosion and the concrete has begun to crumble, Hovezak said. In October 2015, the National Park Service determined Spruce Tree House was hazardous and stopped allowing visitors inside.
Closure of the park’s most popular site is a loss for tourists, but it could be a gain for preservation efforts. Twenty-six tribes and pueblos recognize cultural ties to Mesa Verde and, under federal law, provide insight and direction into how the park operates.
Park officials host annual advisory board meetings with associated tribes, Hovezak said. When crews discovered the rock fall at Spruce Tree House, they consulted tribal preservation officers and asked for input.
“From the Hopi side, Mesa Verde is one of the major sites where Hopi clans lived for a long time,” said Leigh Kuwanwisiwma, director of the Hopi Cultural Preservation Office. “We still have a very strong connection to Mesa Verde, and we still have specific ceremonies that are performed there.”
While his main worry is public safety at the national park, Kuwanwisiwma said there’s more at risk than a crumbling landmark.
“The concern is the destruction of the village itself, of Spruce Tree House,” he said. “It’s what the Hopi call footprints. We were a migrating people, and events are still remembered through burials, petroglyphs, trails.”
Though enclosed inside a national park, Mesa Verde actually is part of a larger narrative told by the Pueblo people, Kuwanwisiwma said. Neighboring sites like Aztec Ruins and Chaco Canyon—both in New Mexico—tell more of the history.
But people crowding into these ruins to experience ancient history may actually be the biggest contributors to its destruction, said Hovezak, who oversees maintenance and repair of 54 archaeological sites at Mesa Verde. While weather is the main culprit, visitors do take a toll on the ruins.
“Really, weather is the major cause of deteriorating with moisture, snowfall and the freeze-thaw cycle,” he said. “But visitors do play a role. If you get a lot of vibrations from people walking on things, over time it will break down.”
Hovezak estimates Spruce Tree House will be closed for three or four years as the National Park Service embarks on a massive, multi-million-dollar engineering plan to stabilize the arch. Meanwhile, he recommends visitors at any cultural sites recognize that ruins are fragile and precious.
“These are irreplaceable heritage resources,” he said. “They are vitally important educational resources, and they are also vitally important to the heritage of the people who used to live there.”