article_snippet: The National Park Service had posted signs at the site on Thursday warning hikers that a fissure along the top of Arch Rock may have weakened the cliff and that walking along the edge was potentially dangerous.
article_snippet: The National Park Service had put up signs on Thursday that warned about a fissure, seen in this undated photo, along the top of Arch Rock that could have weakened the cliff .
highlights_snippet: The National Park Service had warned visitors two days before about a fissure that had opened up on Arch Rock, possibly weakening the cliff .