Zion National Park rangers have concluded that a botched rappel caused climber John Christensen to fall to his death from the 1,200-foot face of Angel's Landing.

The Jan. 1 fatality was Zion's first serious technical-climbing accident in the 30 years rock climbers have been allowed to scale the park's sandstone faces.No one saw the 36-year-old Provo man fall while solo-climbing Angels Landing, but the gear harnessed to the victim suggested he rappeled off the end of one of the two ropes he was using, said National Park Service investigator Dave Bucchello.

Another possibility is a falling rock struck Christensen, causing him to lose his grip on the ropes.

"There's no 100 percent certainty because there were no witnesses and it was in darkness," Bucchello said. But the rope arrangement Christensen was using, which included a special rappel device, conclusively indicates he fell on the descent, rather than on his way up a relatively easy route known as Prodigal Sun.

Investigators believe Chris-tensen reached the top of Angel's Landing late on the night of New Year's Day. Rather than take the long walk down, Christensen apparently opted to rappel.

Christensen employed two 200-foot ropes, one 11 millimeters thick, the other 8 millimeters. Both were used for the rappel in which their ends were tied together and fed through anchors secured to the rock.

Great care is required while descending because the smaller rope will feed through the rappel device faster than the fatter one because its smaller surface area produces less friction, said Bucchello.

After Christensen was reported overdue, searchers found his body at the base of Angel's Landing. About 30 feet of the thicker 11-millimeter rope remained attached to the rappel device, Bucchello said. The investigator estimated Christensen fell between 600 and 800 feet.

Rappelling off the end of the rope is the most common cause of rappel fatalities, followed by failures of the anchor points.