Petrified wood etc

When we did the helicopter flight over Grand Canyon we also flew over part of the Painted Desert. It stretches in a narrow crescent-shaped arc about 200 km long and the exposed mudstone and sandstone looks like a layered cake. It's very colourful and the erosion is still happening because in Arizona they have monsoon rainfall events.

Scientists have found lots of interest in the Painted Desert because it's Late Triassic and they keep digging up or finding exposed fossils. The fragile environment, even down to the lichens that cover the surface, is totally protected.

We went to see a section of the desert that is now in the Petrified Forest National Park in Arizona.

I nearly stepped on a living creature there, a Striped Whipsnake. That's the second snake I've nearly stepped on in the US! Luckily it's nonvenomous but it gave me a fright. And it's name is certainly appropriate because it is a very fast mover, very slim and active. I had no chance to get a photo.

People have been living in the area for thousands of years. We saw the remains of several pueblos that were established about 1000 years ago, and the rock carvings (petroglyphs) nearby. There are thousands of petroglyphs throughout the south-west  but the meaning or symbolism of most of them has been lost. As with all rock decorations anywhere in the world it still amazes me to think that someone long ago sat there chipping or painting the pattern into the rock.

Petroglyphs

Then we drove down to the southern section of the park where there are conifer forests lying on the surface of the ground, petrified into quartz rock. The trees are huge, amazingly heavy and dense and some of the exposed surfaces are stunningly colourful. The logs were buried whole but because of the stresses of erosion and earth movements have broken into vertical sections, just as if they've been sawn apart, but I was told that quartz crystals always break at  90 degrees. The colour part comes about because the quartz also had iron-rich minerals in it. We were stopped as we exited the park to ensure that we weren't taking any pieces of rock with us - it must be a real problem but some local businesses are selling fragments that have come off private properties. 

This cross-section is about 50 cm across and took about three days to cut and polish. It was in the information centre at the park.