[KIDS] Trees Made of Stone?

Petrified Wood Forest | Readorium

A petrified log in Brazil. Image by Sergio Kaminski https://commons.wikimedia.org/wiki/File:Parque_paleobot%C3%A2nico_de_Mata..JPG

Trees: you probably see them every day. They are leafy, tall and woody, right? Except that in certain places around the world, you can find forests with trees made of stone! The Petrified Forest National Park in Ariozona, for example, boasts many such trees! Hard to believe, isn’t it?

Of course, the trees didn’t grow that way. They started out like normal trees. After dying, the trees went through a process called petrification [PET-rif-i-cay-shun]. The word “petrification” comes from Latin, and means “turn to rock”.

How Does Wood Petrify?

Petrified Wood Forest | Readorium

This log from Arizona is actually made of stone! Image by Michael Gabler. https://commons.wikimedia.org/wiki/File:Polished_slice_of_petrified_wood.jpg

Petrification is not fully understood, because scientists haven’t been able petrify wood in a lab. However, they have been able to study it in nature.

Petrification doesn’t happen overnight. It takes millions of years. It begins with a tree dying. The tree is washed away and settles into a stream or river and becomes covered in sediment [SED-i-ment]. Sediment is tiny pieces of rock and sand that settles to the bottom of water.

Because the tree is now underwater and covered in sediment, no air can reach it. This absence of air slows down the rotting process a LOT. The tree is preserved [pre-ZERVD], or kept in its original state.

After this, one of three things can happen. The tree can fall to pieces. The tree can be crushed by the weight of sediment and slowly turn to coal. Or the tree can become petrified! Minerals in the sediment, often the mineral quartz [KWORTS] are absorbed by the wood. As more and more minerals are absorbed, they slowly replace the wood itself. Sometimes, this replacement happens slowly enough that the structure of the wood, with all its cells and rings, is perfectly preserved!

Petrified Wood Forest | Readorium

A slice of polished petrified wood. Image by Daniel Schwen https://en.wikipedia.org/wiki/File:Petrified_wood_closeup_2.jpg

Petrified Wood: Natural Beauty

Petrified wood can be really beautiful. It is sometimes used to make jewelry! In the words of the National Park Service:

Each piece is like a giant crystal, often sparkling in the sunlight as if covered by glitter. The rainbow of colors is produced by impurities in the quartz, such as iron, carbon, and manganese.

However, we need to be careful when visiting parks that have petrified forests! Parks don’t allow visitors to take any petrified wood from them, to prevent loss of the wood, and to make sure that everyone can keep enjoying the parks!

If you enjoyed this article, you might like to read some of our other articles on the rocks and the earth: The Earth’s Own Force-Field and Planets, Comets, Meteors, Oh My: Rocks in Space.

 

Where We Got Our Information

Northern State University

https://www3.northern.edu/natsource/earth/Petrif1.htm

The National Park Service

https://www.nps.gov/pefo/faqs.htm

https://www.nps.gov/pefo/learn/nature/petrified-wood.htm

 

 

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