Which US national park preserves a large area of petrified wood from the Triassic period?

Petrified Forest National Park preserves a large area of petrified wood from the Triassic period.

The park lies in northeastern Arizona and is famous for fossilized trees buried in river sediments during the Late Triassic, roughly 225–207 million years ago. These sediments belong mainly to the Chinle Formation, which also creates much of the region’s colorful Painted Desert landscape.

Petrification occurred as silica-rich groundwater, likely derived partly from volcanic ash, moved through buried logs. Silica gradually replaced organic material with quartz while preserving the trees’ original shapes; iron and other minerals produced the striking reds, yellows, purples, and grays.

A common mix-up is assuming petrified wood is simply ancient wood turned to stone instantly. The process took place gradually underground. The park also protects fossils of plants, reptiles, amphibians, and early dinosaurs, along with archaeological sites connected to Ancestral Pueblo communities. It became a national monument in 1906 and a national park in 1962.