Fun: The Petrified Forest

The Petrified Forest

Imagine, if you will, that it is 3.4 million years ago, and you are standing in a tall grove of redwood trees, surrounded by ferns, in a prehistoric Calistoga, California. There are mammoths, and giant tree sloths and saber-toothed cats wandering about in the world these days…along with other, more familiar animals like armadillos, opossums, hummingbirds, horses, tapirs, and deer–but no humans. We won’t show up for another million and a half years, give or take a few hundred thousand years.

Imagine that you can see a huge, smoldering volcano off to the northeast. Suddenly, the volcano erupts in a cataclysm of smoke, lava, and ash. The ash cloud covers everything, burying the huge redwood trees. The eruption continues for weeks, burying the trees deeper and deeper in layer after layer of volcanic ash. Thousands and thousands of years pass, and the ground becomes saturated with water containing silica (dissolved silicon and oxygen from the layers of ash). One by one, the molecules of silica fill the voids created from dead tree cells, replacing the molecules of the wood, turning the trees into solid silica…quartz…stone.

That is what happened over a vast geologic time scale to create the petrified forest in our very own backyard. You can visit these amazing tree-rocks by taking a quick trip to the petrified forest that now lies only 20 minutes from Santa Rosa, nestled in the hills between Santa Rosa and Calistoga. It is home to the world’s largest petrified trees, the now extinct Sequoia langsdorfii.

Not So Anicient History

Years ago prospectors collected the fossilized wood as a curiosity, but the location didn’t become commercial until a prospector known as “Petrified Forest Charley” dug up an entire tree in 1871 and began charging admission to see the fossilized trees. It was during this time that Robert Louis Stevenson visited the site and wrote about Charley and the petrified trees. The site was taken over by Ollie Bockée and her husband in 1914, and today, her heirs, the Hawthorne family, run the site.

There is a small admission to visit the forest, but it is well worth the price to see these ancient trees that sometimes sparkle in the sunlight from the quartz. You can either walk a half mile trail on your own, or do the “Meadow Walk” on a docent-led tour.

Walking the Forest Path

As you walk the trail, you will see petrified trees that look like someone had cut them with a saw. They weren’t. Petrified wood is mostly silica (quartz), and even though the logs are harder than steel (between 7 and 8 on the 1-10 “Moh scale”), they are also brittle. After the trees petrified, but while they were still encased in matrix rock, they cracked. And since silica naturally breaks on a clean angle, the cracks are mostly straight.

When we visited the petrified forest, we walked the “Main Trail,” which showed off many nice petrified trees, and also had beautiful scenery. Besides green grass, wildflowers, and live trees, the walk also featured several wood sculptures. But the main feature was the fossilized wood. You could examine them closely, touch many of them, and even stand on some of them. Many had names like, “The Pit Pine Tree,” “The Queen of the Forest,” and “The Robert Lewis Stevenson Tree,” which is over 8 feet in diameter. We also saw many lizards sunning themselves and doing push-ups on the rock logs.

For those who are interested in rock collecting, petrified wood also makes a beautiful, collectible stone, which can be made into beautiful jewelry. The types of petrified wood vary almost as much as gemstones. Petrified wood can look like opal, or agate, or any number of other types of stones. The exciting thing about it is that you can still see the rings of the tree, as it existed over three million years ago.

So the next time you find yourself out Calistoga way, take some time to stop by the petrified forest and visit these ancient arboreal fossils. You’ll be glad you did.

by Peter Rogers