And monument officials say it may be years before funding is available to rebuild the structurally weak center located 20 miles east of Vernal.
Wednesday's shutdown was sudden, but soils and structure problems were recognized as early as 1993 and extensively detailed in a 2003 report.
The visitor center - it houses the world's largest quarry of Jurassic Period dinosaur bones - opened June 1, 1958. Built against a mountainside, its 50-by-150-foot north wall exposes some 1,500 fossils of 11 types of dinosaurs.
About 300,000 people visit the eastern Utah facility each year.
But new studies indicate a small earthquake could collapse the already-shaky structure.
"Over the years, the soils have expanded and contracted," said monument Superintendent Mary Risser. "That has played havoc with the structural integrity."
Two other visitor centers - one in Utah and one in Colorado - remain open in the 210,000-acre national monument.
The Quarry Visitor Center, listed as a National Historic Landmark, was scheduled for a major reconstruction in 2004. But cuts in National Park Service budgets stalled those plans, Risser said.
The $6.3 million to $7.3 million reconstruction was pushed back to 2010. But that time frame is now in question.
"I have no idea when this would score highly enough to get re-funded," Risser said.
Federal officials recognized as early as its completion 48 years ago that soils under the quarry building could lead to problems. A 1993 National Park Service report raised additional alarms about soil drainage and settling.
But an October 2003 Park Service study outlined serious structural deficiencies and underscored the need for prompt action.
"It could be argued that in its current state, the Quarry Visitor Center is marginally habitable," the three-year-old report states. "The building is founded on a shallow foundation system that is not strong enough to resist soil swelling and uplift."
At the time of the 2003 study, a calamity was not out of the question.
"Although the structural system is tenuously stable at present, unchecked deterioration of the distressed roof, floor deck, or a buckled interior wall may result in sudden redistribution of loads and a chain reaction of material failures."
The latest report, however, raised the level of alarm, leading to Wednesday's closure.
That study, initiated in May, revealed that the structure was "a very serious life-safety hazard," Risser said. "We have strong concerns that the whole thing could collapse."
Dinosaur National Monument is the outgrowth of a 1909 discovery by paleontologist Earl Douglass. President Woodrow Wilson designated the find as a national monument in 1915.
Monument staff will continue to provide guided geological hikes, as well as tram tours to the overlook of the confluence of the Green and Yampa rivers.
"We have scenic beauty to compare to any other national park," Risser said.
Visitor-center problems identified in 2003 report:
* Floors heaved as much as 8 inches.
* Windows, under pressure, broke "spontaneously."
* Toilets flushed wastewater onto floors.
* Walls crushed between floor and roof beams.
* Viewing gallery dropped 12 inches.
To view the entire 2003 report, visit