In east central Arizona's Petrified Forest National Park you'll find an odd sight: Large sections of fossilized trees strewn across the dry desert floor. The Navajo believed them to be the bones of a giant killed by their ancestors, while the Piute saw them as arrow shafts from the thunder god. In 1888 Smithsonian curator F.H. Knowlton identified them as a species of extinct trees he called Araucarioxylon arizonicum, but scientists now believe the term actually describes many species of extinct trees that flourished in the region some 200 million years ago [sources: Knowlton, NPS, Conover].
They were giant conifers with trunks measuring 10 feet (3 meters) in diameter that once reached up to 194 feet (59 meters) into the sky before they were toppled by ash and debris flows caused by a nearby volcanic eruption [source: Ash and Creber]. It was these destructive flows, however, that encased the trees and crystallized their remains, ultimately preserving them for us to enjoy millions of years later [source: Conover].
Interestingly, the fossils themselves almost went extinct, so to speak, because of rampant collecting. It all started when General William Tecumseh Sherman requested an expedition to collect two large specimens for the Smithsonian. After that, opportunistic businessmen swarmed the area, hauling off sections of the fossilized trees to craft into things like tables, tiles, jewelry and mantels. While the creation of a national monument in 1906 and a national park in 1962 helped slow the plundering, an estimated 12 to 14 tons of petrified wood is illegally snatched each year by tourists [source: Conover].