Air Date: Week of September 28, 2001

This week, facts about the first petrified forest. One hundred and fifty years ago, an army captain looking for a way through the desert, came upon one of the largest areas of petrified trees in the world.

Transcript

CURWOOD: It's Living on Earth. I'm Steve Curwood. One hundred and fifty years ago U.S. Army Captain Lorenzo Sitgreaves was leading a geological survey to find a railroad route through the desert of Eastern Arizona. What he discovered in the process was the nation's largest petrified wood forest. A geologist on Captain Sitgreaves' team immediately recognized the fossils as conifer trees that had died about 225 million years ago. The trees had been washed down a stream and buried in volcanic ash and silt. Over time the trees became petrified, as water seeped into the logs and replaced wood fiber with silica, which then crystallized. Captain Sitgreaves had seen petrified wood before, but never so much in one place. Whole petrified tree trunks were strewn over the desert.

When the railroad was completed, much of the wood was carted away to the East Coast, where it was used in building fine furniture. In the 1890s, people used dynamite to blow apart larger logs and get at the gems inside.

To protect the wood, John Muir and Teddy Roosevelt worked to get the area declared a national monument, in 1906, and it became a national park in 1962. But the theft of petrified wood remains a problem today. Park officials say about 12 tons go missing from the park each year. Still, every year, about 100 pounds of petrified wood is mailed back to the park by visitors who later felt maybe just a little bit guilty about stealing it. And that's this week's Living on Earth Almanac.