The history of the Petrified Forest, designated a national park in 1962, is one of commercialism and vandalism.

In the 1890s, a mill was erected in the park to crush the stones into industrial grinding powder.Before it was named a national monument in 1906, visitors removed the stones by carloads, polished them up and sold them to tourists.

In that regard, not much has changed. Today, petrified wood found outside the park boundaries is shined up for the tourist trade at the park's two visitor centers.

The wood, of course, is the main attraction here, and there is plenty of it. You can do just about anything with it but pocket it.

This 93,533 acres of parkland are located near the towns of Chambers and Holbrook, off Interstate 40. A $5 admission (good for a week) will get a carload inside, and a number of points of interest offer a full day of sightseeing.

The first is the Painted Desert Rim Trail, which winds between Tawa and Kachina Points. While the bands of purple, scarlet and pink tints look beautiful from the air-conditioned comfort of a car, visitors need to feel the prickly heat, crunch the soft clay beneath their feet and allow the wind to wipe their sweaty brow.

Here, too, you can check out the petrified wood for the first time.

The biggest concentrations of petrified wood, though, are at Jasper Forest Overlook, the Crystal Forest, the Long Logs and the Giant Logs' Loops.

These dead forests of petrified trees, which look similar to today's sequoias and pine trees, were petrified 225 million years ago, during the late Triassic Period - the beginning of the Age of the Dinosaurs.

At that time, northeastern Arizona was a vast flood plain with lush ferns and many trees, which gradually died, fell to the ground, and were washed away to nearby swamps where they were buried by clay and silt.

Silica, contained in the ash of nearby volcanoes, combined with the swamp water to form microscopic quartz crystals inside the wood, to slowly petrify the logs. Other minerals that seeped in along with the silica gave the wood its spectacular colors.

In time, the clay was worn away by the rain and wind, revealing the petrified logs.

Another attraction at the Petrified National Forest is the Blue Mesa Badlands, appropriately named because they truly look blue - or gloriously purple - in the morning sun. The afternoon sun makes them look more granite-colored.

While these Badlands can be seen from the road above, it can be an experience at the bottom, too, which requires some hiking. Here you can see where rainwater has raced down the hillsides, creating intricate patterns and miniature ravines. The volcanic ash crumbles easily in your fingers, and in terms of geological time, the Blue Mesa Badlands won't be here for long.

What looks impregnable at a distance is ephemeral up close.

There is only one attraction to which tourists are denied access, although they can see it from a short distance away. Despite all the literature to the contrary, visitors no longer can walk down to one of the main features of the park, Newspaper Rock, where the ancient petroglyphs (rock paintings) of the Anasazi Indians are located.

An art form created by the Anasazi, or ancient ones, the petroglyphs were made by chipping through the desert varnish, which is a dark mineral stain covering the lighter rock surfaces.

Three years ago, a cave-in closed the trail to Newspaper Rock and it was never cleared. Vandalism had been a problem before the cave-in, so park people decided not to re-open the trail in hopes of discouraging further vandalism, according to Glenn Gossard, a park ranger.

The initials of vandals mar the prehistoric etchings of the Anasazi.

But he points to other petroglyphs that can be found among the rocks at the base of the Puerco Indian ruins, another feature of the park. Here, the Anasazi built a 76-room pueblo centuries ago, and this was partially reconstructed by the Civilian Conservation Corps in the 1930s.