Large petrified tree known as Onyx Bridge snaps into pieces at Arizona national park

One of the world’s most “dramatic” examples of a petrified Triassic-era tree has lost “its battle against gravity” and collapsed, according to the Petrified Forest National Park in Arizona.

Known as the Onyx Bridge, the fallen but intact tree was iconic as a massive fossil that resembled a natural bridge, the park said in a Wednesday Facebook post.

The bridge was recently discovered snapped apart, and experts believe it happened sometime in December.

Park officials lamented the fallen “icon” with before and after photos, showing the longest span of the tree had broken into pieces and was lying in the gully it once spanned.

“There were cracks for many years and a couple of spots where it sagged, but the big break happened just two months ago,” the park said.

It’s not clear when park officials discovered the change — the bridge is in a remote area — but the damage is credited to natural causes and not vandalism. The 30-foot-long conifer is believed to be 210 million years old, making it overdue for cracking, the National Park Service reports.

“Onyx Bridge is a dramatic example of petrified wood eroding out of the Black Forest Bed of the Chinle Formation,” the NPS says.

“The Chinle Formation was deposited over 200 million years ago during the Late Triassic Period. The colorful badland hills, flat-topped mesas, and sculptured buttes of the Painted Desert are primarily made up of the Chinle Formation.”

The tree’s appearance as a natural bridge was a bit misleading. Though it seemed to have fallen across a gully (or wash), it was actually there before the gully, experts say. Centuries of erosion uncovered the tree and eventually washed the earth from beneath it, building a bridge in reverse, the National Park Service says.

“More than 200 million years ago, flourishing trees and vegetation covered much of this area of Northeastern Arizona,” Visitarizona.com reports.

“But volcanic lava destroyed the forest, and the remains were embedded into sediment comprised of volcanic ash and water. Erosion set the logs free millions of years later, revealing the petrified wood — made mostly of quartz — that Arizona visitors gather to see,” the site says.

This story was originally published February 4, 2021 at 1:56 PM with the headline "Large petrified tree known as Onyx Bridge snaps into pieces at Arizona national park."