Arizona Highways Online
Petrified Wood - Araucarioxylon arizonicum
By Kathryn Eastlick
About 225 million years ago, a lush forest covered the area of northeast Arizona we now call the Petrified Forest. Back then, 200-foot-tall conifers ruled the land, but when southern volcanic mountains erupted, the trees toppled and were swept into waterways. Streams deposited logs into marshes where they were covered with mud containing volcanic ash. Buried under layers of sediment, the logs waited patiently for the day when erosion would release them from entombment.
The logs remained buried for millions of years, undergoing the long, arduous process of petrification. Eventually an ocean moved in and covered the area, depositing even more sediment on top of the logs. Then about 60 million years ago, the ocean moved away and flowing rivers began to remove 2,600 feet of sediment, eventually exposing the petrified wood that decorates the Petrified Forest National Park.
The key ingredients for petrified wood are wood, water, mud and volcanic ash. But don’t expect to whip up one of these lovely logs for yourself unless you have a few million years on hand. Petrification begins when a hapless log gets buried in mud containing volcanic ash, which releases chemicals during decomposition. As water saturates the log, these chemicals react with the wood and form quartz crystals. By itself, quartz crystal is colorless, but minerals in the water, such as iron or manganese, give the quartz red or pinkish hues, respectively. Over time, the quartz crystals completely cocoon the log, slowly turning it into stone.
Arizona’s Petrified Forest contains one of the world’s largest concentrations of petrified wood, which range in size from gigantic logs to tiny chunks.
Visitors to the national park may find themselves tempted to snag one of the ancient treasures as a souvenir, but park officials make sure to warn guests of an alleged curse that brings bad luck to thieves. Apparently the warning doesn’t scare away everyone – some park officials estimate they lose 12 to 15 tons of petrified wood every year.
But park officials also find themselves the recipients of packages containing pieces of petrified wood and confessional letters. Stacks and stacks of letters uphold the legend of the curse, swearing that since stealing a nugget, all sorts of terrible things have happened – including divorce, disease and plain ol’ back luck. Park officials are happy to propagate the myth in hopes of discouraging theft. If rangers do catch violators (sometimes stuffing rocks in their undergarments), the park’s tough no-tolerance policy dictates a minimum $275 fine. Some fines have been as much as $3,000.
In some areas of the Petrified Forest, 300 feet of sediment still conceals never-seen petrified treasure. As wind and water continue the slow process of erosion, the soil will wear away to reveal more and more petrified wood, which also has the honor of serving as Arizona’s state rock and state fossil.
|
|
 |
