- Grade Level:
- Upper Elementary: Third Grade through Fifth Grade
Did you know that Yellowstone has groves of petrified trees scattered across the park?
Around 50 million years ago, Yellowstone was home to forests of sequoia, maple, magnolia, and oak trees.
Volcanic eruptions buried the forests in ash, mud, and debris. Silica in the ash dissolved in the groundwater and seeped into the tree, filling the spaces among its cells. The water evaporated and left behind the silica. The tree hardened to stone (petrified) from the inside out.
What You'll Need
- 1 tablespoon of Epsom salt (magnesium sulfate)
- 2 tablespoons of water
- 1 paper towel (folded into quarters)
- 1 plate
What To Do
- Mix the Epsom salt and water on the plate. Roll the paper towel into a log or tube shape. Place the paper towel on the plate.
- Wait for the Epsom salt and water mixture to disappear. It may take up to a week to dry completely.
- Observe! What do you notice about your paper towel log?
Why It Works
Wood (your paper towel log) petrifies, or turns to stone, as dissolved minerals (your Epsom salt and water mixture) are absorbed and the minerals slowly replace the wood cells.
Printable version of the petrification station activity.
Last updated: August 16, 2018