From Wood to Stone

Approximately 225 million years ago during the Triassic Period, a floodplain here was littered with fallen trees, and periodic flooding buried the logs beneath layers of silt. Over time, silica-laden waters filtered through these deposits and petrified the wood by encasing the trees’ organic material with minerals. Iron oxides gave petrified wood its distinctive red, yellow, and orange hues; manganese oxides produced blues, purples, and deep blacks; and the original carbon produced shades of gray. Centuries of erosion washed away concealing sediment deposits and exposed these remnants of Triassic woodlands. Although the processes that created petrified wood here ceased millions of years ago, geologic forces similar to those of the Triassic period still shape Earth’s surface and may create the preliminary conditions for future petrification.

Arizona · United States