Giant Logs Area
Petrified Forest National Park, Arizona

Some 225 million years ago this was a large floodplain crossed by numerous rivers and streams. For years, the large ancestral pines that grew here fell into the rivers and became petrified over time. Buried in the sands of the river, groundwater carrying silica slowly replaced the organic materials of the wood with inorganic materials. Apparently, this wood was not buried deep enough, or quickly enough, for the temperature and pressure to build high enough to make coal out of the woody deposit before it was completely petrified. Over time, that silica crystallized into hard quartz that has the same properties and lifetime as any other very hard rock. The Chinle Formation here is some 1,800 feet thick and there are Triassic and Jurassic era fossils and petrified woods encased throughout the formation.

After thousands of years of burial, uplift, exposure and re-burial, the countryside evolved into the high Arizona tableland we see today. And the same forces that sculpted and shaped the Painted Desert have also exposed the petrified forest and continue to bring more and more of that ancient petrified material to the surface.

The Rainbow Visitor Center is at the foot of the Giant Logs Trail.