Agate Bridge, Petrified Forest, Arizona
N 34° 53.555 W 109° 47.639
12S E 610197 N 3861794
Quick Description: A natural bridge built by a 225 mil. years old petrified tree
Location: Arizona, United States
Date Posted: 1/11/2007 3:38:37 AM
Waymark Code: WM14DJ
Yes, this is a natural arch, though – unfortunately – it doesn’t look like one anymore. The location is Petrified Forest National Park, where, 225 million years ago, a lot of tall trees were washed into a floodplain, where a mix of silt, mud and volcanic ashes buried the logs. The sediment cut off oxygen and slowed the logs decay. Silica-laden groundwater seeped through the logs and replaced the original wood tissues with silica deposits. Eventually the silica crystallized into quartz, and the logs were preserved as petrified wood.
Later, centuries of scouring floodwaters washed out the arroyo, or gully, beneath this 110-foot long petrified log and formed a natural bridge. The petrified log, harder than the sandstone around it, resisted erosion and remained suspended as the softer rock beneath it washed away.
Enthusiastic visitors fascinated by the bridge worked to preserve it through the establishment of Petrified Forest National Monument in 1906. Conservationists felt this ages-old natural bridge needed architectural support and in 1911 erected masonry pillars beneath the log. In 1917 the present concrete span replaced the masonry work.
Current National Park Service philosophy allows the natural forces that create unusual features to continue. If discovered today, Agate Bridge would be left in its natural state.
This is what it looks like
This is what it should look like
We have tinkered a little bit with the picture on the right to show you what the bridge would look like unsupported. However, supported or not, sooner or later the natural forces that created the bridge will force it to fall and eventually it will look like all the others in nearby Crystal Forest. Enjoy it while it lasts (which might as well be for another million years).
Click on any picture to get larger images