How Did These Petrified Logs Get ‘Minimize’?

Why do the petrified logs seem like somebody minimize them with a noticed?

Petrified wooden is usually silica—quartz. The logs are very exhausting (7.eight on the 1-10 Mohs hardness scale!), however brittle. After petrification, however whereas the logs have been nonetheless encased in matrix rock, the logs cracked underneath stress. Because the logs eroded out, from gravity and ice wedging, the cracks widened and segments separated. Silica naturally breaks on a clear angle.

To reply Mr. Klages’ query, we turned to Invoice Parker, the park paleontologist we featured within the difficulty. “The fossilization course of itself is pretty complicated,” he says, however it goes one thing like this:

A tree dies, falls over and is buried in a river channel or floodplain, underneath layers of mud, sand and gravel. Within the groundwater desk, the tree turns into saturated like a sponge and expands. The water, sand and gravel minimize off publicity to oxygen, so the tree does not rot. Volcanic ash within the water breaks down, and the silica that was within the ash goes into answer — forming silicic acid, which enters the waterlogged tree and interacts chemically with the wooden, altering it to silica and replicating the options of the wooden. Over time, you find yourself with a silica duplicate of the tree.


The method truly occurs pretty shortly, geologically talking — inside “a number of 10,000s of years,” Parker says.

Ultimately, the log leaves the groundwater desk and goes by way of a strategy of “dewatering” and recrystallizing, this time as strong quartz. “Thus, all the Triassic logs at Petrified Forest now consist virtually solely of quartz,” Parker says. This course of takes for much longer — tens of tens of millions of years, in line with the fossil document.

However why achieve this most of the logs seem “reduce”? It has to do with how they obtained to their current location, Parker says: “About 60 million years in the past, forces of geology began the uplift of the Colorado Plateau. This space went from deeply buried to being uncovered and raised greater than 1 mile above sea degree. As a excessive level, it’s constantly eroding away, exposing previous rocks and their fossils, such because the petrified logs from the Triassic.”

Photograph Petrified Forest Nationwide Park

So the motion and erosion of the land is what brought about the logs to interrupt. And the inside surfaces the place they’ve damaged are flat as a result of quartz does not break neatly throughout its crystal faces, so as an alternative it snaps throughout the log’s shortest space throughout — type of like whenever you snap a bit of chalk, Parker says.

“These logs are pure quartz, and to chop them would require a diamond noticed,” he provides. “Rock outlets use these saws to chop log parts and polish them on the market,” however right here at Petrified Forest, this has occurred naturally over very lengthy durations of time.”

The above submit is reprinted from Arizona Highways


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