The Agate Bridge in the Petrified Forest National Park is a 110-foot long petrified log across a gully washed out by centuries of flood waters. The stone log, which was harder than the sandstone around it, resisted erosion and remained suspended as the softer rock beneath it washed away.
After the Petrified Forest National Monument was established in 1906, conservationists felt the bridge needed architectural support. In 1911 masonry pillars were erected beneath the log. In 1917 the pillars were replaced by the concrete span seen in the picture above.
Current National Park Service philosophy allows the natural forces to continue to act upon unusual features. If it was discovered today, the Agate Bridge would be left in its natal state. Even with the support placed under it nearly a century ago, the same forces that created the Agate Bridge will eventually cause it to fall.
For another perspective of the Agate Bridge click HERE.