What Is an EarthCache?
An EarthCache is a special kind of geocache that teaches you about a geological feature of our planet.
There is no physical container or logbook to find — instead, you make observations, answer educational questions, and learn something new about the Earth in the process.
EarthCaches are developed in partnership with the Geological Society of America, and every one of them helps geocachers connect with the natural world in a deeper way.
Logging Tasks
To claim a find, please send your answers and required photo to the cache owner through Geocaching.com (do not post answers in your log).
All reasonable efforts will be accepted — this is meant to be fun and educational!
1. Observation: Locate the large piece of petrified wood near GZ. Describe its overall appearance.
• What stands out about its texture, color, or shape? Does it resemble wood, stone, or something else entirely?
2. Composition: Using the color chart below, identify at least three colors visible on this specimen.
• Which minerals are likely responsible for those colors? Which color appears most dominant?
3. Size & Weight Estimate: Estimate the specimen’s approximate dimensions (height × width × length).
Using the information that petrified wood can weigh 160–200 lbs per cubic foot, roughly how much might this specimen weigh?
4. Geological Interpretation: Based on what you observe and the information on the nearby sign, what conditions (e.g., volcanic ash, floodplain, sediment burial) do you think might have led to this specimen becoming petrified?
Photo Requirement:
Take and upload a photo of yourself or a personal item (such as a GPS, hand, or notebook) with the petrified wood visible in the background.
The purpose of this photo is to confirm your observation of the geologic feature — please respect the protective chain and do not touch or climb on the specimen.
Earth Science Lesson
Wait… That’s Not a Dinosaur?
At first glance, this impressive specimen might look like a fossilized dinosaur bone — but it’s actually petrified wood! Don’t worry if that surprises you; even experienced fossil hunters can mistake it at first sight.
How Does Wood Turn to Stone?
The process of petrifaction begins when trees are buried in water-saturated sediment or volcanic ash.
In these low-oxygen environments, decay slows dramatically. Over time, mineral-rich water flows through the sediment, filling the wood’s cellular spaces with minerals such as silica, quartz, or calcite.
This can occur in two main ways:
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Per-mineralization: Minerals fill in pores and empty spaces within the wood.
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Replacement: The minerals gradually replace the organic material cell by cell, preserving the tree’s original structure in stone form.
Millions of years later, what was once wood has literally become rock — often preserving the fine details of the original tree.
Why So Many Colors?
The vivid hues of petrified wood come from trace elements in the groundwater during fossilization.
| Element |
Color(s) Produced |
| Carbon |
Black |
| Iron Oxides |
Red, Brown, Yellow |
| Manganese |
Pink, Orange |
| Copper, Chromium, Cobalt. |
Green, Blue |
| Silicon Dioxide |
Clear, White, Grey |
Each specimen is unique — like a natural mosaic shaped by time, chemistry, and geology.
Why Is It So Heavy?
When minerals replace organic material, they make the fossil far denser than wood. While normal wood weighs around 30 lbs per cubic foot, petrified wood can weigh up to 200 lbs per cubic foot! That’s one reason why large specimens, like this one, are displayed behind protective barriers — they’re extremely heavy and fragile.
Where Can You Find Petrified Wood?
Petrified wood is found worldwide — from the deserts of Arizona to the volcanic plains of Iceland.
In Canada, you can find it:
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In the badlands of southern Alberta (it’s the provincial stone)
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On Axel Heiberg Island, Nunavut, home to an ancient petrified forest
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Along the North Saskatchewan River near Edmonton
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In Newfoundland’s Blanche Brook, where examples are over 300 million years old
Collectors value these specimens for their natural beauty and the story they tell about our planet’s past.
A Note from the Cache Owner
This EarthCache has a higher difficulty because it asks you to observe, infer, and estimate — not just read a sign. It’s designed to be fun, visual, and educational, even without touching the specimen. Reasonable effort counts — enjoy learning about this incredible example of ancient Earth science!
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