A section of prehistoric tree at the Petrified Forest in Northern Arizona. HipTravel Mobile in the background.

From Wood to Stone: A glimpse into the Triassic Era

East of HOLBROOK, Ariz. — The trees of the Petrified Forest are not what they seem. In fact, there not really trees at all. They’re stone copies of ancient trees that grew 165 million years before the dinosaurs — back when this area was all floodplain and covered with lush vegetation and forest.

So, are they a study in botany or geology? Actually, it’s both. In the late Triassic era, thousand of trees were washed away by frequent flooding and covered by layers of mud and sediment. Stored underground and protected from decay, the wood absorbed ground water laden with quartz and minerals.

Over millions of years, quartz continued to grow inside, preserving the wood, turning it into very hard quartz stone — so hard that a stone polisher, using a super sharp blade, would need 16 hours to cut through a 3-foot diameter stump.

Pictured above right: Daniel enjoy the log ride atop “Old Faithful,” a 35-foot tree section that weighs 44 tons.

From wood to stone. After 225 million years, it’s no longer wood anymore. Water laden with silica crystals (quartz) encases the tree’s organic material with minerals. Eventually, the silica replaces the wood entirely creating a stone copy of the original wood.

Prehistoric lumberjacks. It would take hundreds of years for park rangers with sharper-than-sharp blades to chop through all that hard quartz stone. Some sections weigh as much as a small Volkswagen auto. Since petrified logs are composed of quartz, they are hard and brittle, breaking easily under stress. As erosion exposed the logs, cracks form and widen. Gravity causes sections to roll away from their original placement.

Newspaper Rock. Petrified Forest adjoins the Painted Desert to the north and creates a 25-mile driving tour that you can make at your own leisure. Along the way, you can see 1,000-year-old petroglyphs carved by Native American Indians. Toward the end of the driving tour, you run across two souvenir shops where you can purchase polished
petrified wood. The Parks Service issues fines for those
trying to steal petrified wood from the park.