Sundance in Crook County, Wyoming — The American West (Mountains)

Petrified Trees

Fossils Give Clues to Wyoming's Paleo-Past

Photographed by Beverly Pfingsten, June 7, 2011

1. Petrified Trees Marker

Inscription. Giant cypress trees growing today in swamps (or forested wetlands), such as these found in Louisiana's Pointe Lake, used to grow in Wyoming back when it was a warm, subtropical swamp - about 55 million years ago during the Late Paleocene epoch. Some of these ancient trees were buried under sediment and turned to stone. the three petrified trees located here were found during coal mining operations at the Eagle Butte Mine near Gillette. They were generously donated by Alpha Coal West, Inc., and transported to this site by the Wyoming Department of Transportation.

Coalification: Turning Swamps into Coal
Vegetation thrives in warm wetlands. As these plants die, they accumulate in a layer of material called peat. Peat generally occurs below the water line where bacteria turn the plants into a dark gel. Over time, the gel gets buried deeper under new layers of plant batter and peat. high temperatures within the earth essentially cook this material over millions of years, driving off moisture and converting the plant residue into the organic, sedimentary rock that we call coal.

Petrification: Turning Wood into Stone
While some trees

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that die in swamps turn into soft coal, others turn into hard stone. Submerged underwater in the muddy, low-oxygen conditions of a swamp, some tree trunks are protected from decay. Silica dissolved in groundwater soaks into the wood. Through a chemical process called petrification, this and other minerals replace the plant tissues, making a crystalline cast of the tree. The orange and red colors seen in these examples indicate the presence of iron oxide, along with silica.

Rings Reveal Age of Tree
The petrified tree next to the front door of the Visitor Information Center has visible tree rings. If you count them, you can estimate its age to be about 300-500 years old - when it died millions of years ago. it died young. The petrified tree near you is much larger and probably lived much longer, but its rings are harder to read. mature cypress trees in this area reached between 1,200 and 1,500 years of age.

Topics. This historical marker is listed in these topic lists: Horticulture & Forestry • Paleontology.

Location. 44° 31.661′ N, 104° 12.346′ W. Marker is in Sundance, Wyoming, in

Photographed by Craig Doda, September 1, 2018

2. Petrified Trees Marker

Crook County. It is on Interstate 90. Marker is at the Wyoming Welcome Center. Touch for map. Marker is in this post office area: Sundance WY 82729, United States of America. Touch for directions.

Regionally, this marker is in the Powder River Basin.

It is also in the American Mountain West,

in the Black Hills,

on the Great Plains,

on the Northern Plains,

and specifically on the High Plains.

Globally, it is in North America,

the Western Hemisphere,

the Western World,

and the Anglosphere.

Historically, it finds itself in what was once the Louisiana Purchase.

Other nearby markers. At least 8 other markers are within 3 miles of this marker, measured as the crow flies: The Custer Trail (here, next to this marker); Rich Colors, Rich Lands (here, next to this marker); Bird of the Black Hills (here, next to this marker); The Vore Buffalo Jump (here, next to this marker); Paha Sapa, Black Hills (here, next to this marker); Matthew S. Driskill (within shouting distance of this marker); a different marker also named Vore Buffalo Jump (approx. 2½ miles away); Understanding Bison Behavior Brought Success (approx. 2½ miles away).

Petrified Tree image. Click for full size.

Photographed by Beverly Pfingsten, June 7, 2011

3. Petrified Tree

Touch for a list and map of all markers in Sundance.

Photographed by Beverly Pfingsten, June 7, 2011

4. Petrified Tree

Credits. This page was last revised on April 16, 2022. It was originally submitted on August 4, 2011, by Bill Pfingsten of Bel Air, Maryland. This page has been viewed 2,227 times since then and 48 times this year. Photos: 1. submitted on August 4, 2011, by Bill Pfingsten of Bel Air, Maryland. 2. submitted on November 22, 2021, by Craig Doda of Napoleon, Ohio. 3, 4. submitted on August 4, 2011, by Bill Pfingsten of Bel Air, Maryland.