Painted Desert and Petrified Forest
I'm on the road again and traveling across northern Arizona. On my way to Flagstaff, I spent some time at the Painted Desert and Petrified Forest National Park. It is an arid landscape where the Chinle Formation has been exposed through centuries of erosion. This formation was deposited about 220 million years ago near the end of the Triassic period. A shallow lake covered this area and sediments from streams and rivers flowing into the area deposited silt with combinations of minerals and other substances. The red tones were formed by varying amounts of iron oxide. The lavender grey tones were usually created by decayed plant and animal matter. The white coloring appears due to volcanic ash. As the the fine grained landscape erodes the colors blend forming a range of pastel hues. The colors appear the strongest in early morning and late afternoon.
The streams and rivers that flowed into the shallow lake covering this area carried the remains of fallen trees. As the remains settled into the mud, the silt bed covering the trees grew thicker and the process of fossilization began.
The area eventually dried out and the process of erosion began. Much of the area of the now exposed land is made up of fine-grained mudstone, sandstone, and clay. The erosion process has exposed the once buried and now fossilized trees.
The organic matter of many of the petrified trees has been replaced with varieties of quartz creating a rainbow of colors in tree trunk cross sections.
