Some information thanks to Wikipedia:
Petrified Forest National Park is known for its fossils, especially of fallen trees that lived in the Late Triassic period of the Mesozoic era, about 225 million years ago.
During the Late Triassic, downed trees accumulating in river channels in what became the park were buried periodically by sediment containing volcanic ash. Groundwater dissolved silica (silicon dioxide) from the ash and carried it into the logs, where it formed quartz crystals that gradually replaced the organic matter. Traces of iron oxide and other substances combined with the silica to create varied colors in the petrified wood.
In Petrified Forest National Park, most of the logs in the park retained their original external form during petrification but lost their internal structure.
Our first stop was to look at the Giant Logs.
We carried on driving through this amazing scenery.
We carried on driving past the Blue Forest and the Tepees.
We stopped where Route 66 use to go through the National Park.
We then had another hours drive on the I40. We seem to be the only car on the road, the rest just trucks!
By the time we got to our hotel it was 9:00 pm. And then we realised we were in a different state in a different time zone. So we actually checked in at 10:00 pm!!
It was a very nice room we checked into.