Have you ever seen the brilliant hues of petrified wood and wondered how it gets its colors?

When trees die, they typically fall to the forest floor, where they decay.

But if they fall in a place without oxygen—in water, a swamp or bog, or are buried by volcanic ash or flood silt—they may not decay.

After thousands or millions of years, water seeps into the pores of the wood, carrying dissolved silica. The silica bonds with the cellulose and replaces it.

Then other mineralized water enters the silica–cellulose framework, where those compounds replace the rest of the organic material.

We’ve found nearly 40 minerals in petrified wood, many containing iron, manganese and chromium, which provide its spectacular red, orange and blue colors.

The lithification process also preserves the physical structure of the tree, sometimes down to the microscopic level.

Eventually, erosion exposes the fossilized logs—some dating back over 300 million years for us to discover...

And they’ve helped us study the long history of tree evolution while providing valuable information about the environmental conditions of the ancient past, such as rainfall, drought, fire and insect populations.

Petrified Forest National Park in northeastern Arizona is one of the most famous sites. Definitely worth a trip, especially in the spring or fall when temperatures are mild, to find beautifully colored windows into the past.