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Roger Weller, geology instructor

Petrified Forest
by Amelia Moheit
Historical Geology
Spring 2010


The Petrified Forest

            One of the amazing wonders of North America is the Petrified Forest, a forest that has literally, been frozen in time, dated as far back as the late Triassic period. This is such an amazing wonder because it gives us a glimpse as to what the continent was like millions of years ago. Terry Wright describes the ancient continent as a Lush redwood forest with strange animals scurrying around, in the book Volcanoes in Eruption. There have been many fossil findings at the Petrified Forest national park. Archeologists find new pant fossils every year at the forest. With the fossils we are able to tell what the weather was like millions of years ago. These are just much different from the desert that it is today.

The Keystone Arch Photographed by T. Scott Williams


Because of the unique difference in climate and volcanic activity, the Petrified Forest was able to form. During monsoon season, water runoff would wash the trees into sandy wash areas and then the trees eventually were covered in sand that contained volcanic ash. The silica in the ash replaced the wood, which caused the trees to petrify. Throughout time, the land would erode leaving the stone forest and the Chinle formation. Not only does the Petrified Forest contain fossil plants, it also has some of the earliest dinosaur fossils from North America. The way that the earth was preserved from the volcanic ash, we are also able to tell the nature of the landscape and the climate. The paleosols, which is the ancient soils, suggest that the climate was either very wet or very dry. Present day climate is much different. Today it is considered a desert ecosystem, with rivers and streams that cut through the rock formations and dry landscape. Some call the environment badlands because it is not the optimal environment to live in, with little rainfall and hot temperatures and heavy winds. Even though this is considered an extreme environment to live in, people have been calling the Petrified Forest home for thousands of years.

There are findings of petro glyphs in the area showing that early humans once lived there. Native Americans had inhabited the area at least ten thousand years ago. The Anasazi, Mogollon, and Sinagua all lived there for a period in their history. The Petrified national park has archeological findings from all of these tribes. There is even a one hundred-room pueblo near the Puerco River. Years later Spanish explores passed through the area and in the eighteen hundreds Lorenzo Sitgreaves, a United States Army Captain, publish his writings about the park. He was the first to do so. Later, people began to destroy the petrified wood to look for gems inside it but had no luck. Shortly after, the state of Arizona made the forest a National Park hoping to end the destruction. The demolishing of the wood had ended but the public was also steeling the wood for their own personal collection.

Even though there is wood for sale to the public from privately owned properties, twelve ton of the petrified wood is stolen every year. The National Park rangers have put up fences and signs alarming the public that there are fines if the wood it stolen. Although much action is taken to prevent theft of the fossil wood, it still occurs.
The Painted Desert photo taken by T Scott Williams/ NPS


Within the Petrified Forest National Park, there is also the Chinle Formation. The Chinle formation is the product of years of river deposits. It is made up of the hills, mesas, and buttes of the Painted Desert. The colorful layers in the formation are the ancient soils; each different color shows the different minerals that exist in the sand. The colors also vary depending on where the water table was at the time the soils were placed there. For example, red soils were able to form when the water table fluctuates because the iron rusted giving it the red coloration. It is said that the Painted Desert got its name from having the same colors of the sunset and it looked like it had been painted there.

Many things make the Petrified Forest national park an amazing wonder of the world, the best one being that it is completely natural. It is a product of the always-changing world we live in. Some may think it is a gift because of the beauty of it. To the uneducated eye, the forest may seem like just a beautiful place to feast your eyes upon, but to those of us who know the forest is like a time capsule waiting to be unlocked. The sequence of events that took place to give us the Petrified Forest are a rare happening and I think that everyone should visit there to appreciate that at least once in their lifetime.




Works Cited

National Park Service coordinator. The Petrified Forest. <>

            April 20, 2010

Williams, T. Scott. Photographs. The Petrified Forest. . <>

Wright, Terry. The Petrified Forest <>

April20, 2010.