PETRIFIED FOREST NATIONAL PARK, ARIZONA

The petrified forest is located in a high, dry tableland which was once a vast floodplain crossed by many streams. The trees fell and were washed away by the streams into the floodplain. There they became waterlogged and sank to the bottum of the stream. The logs were then covered by layers of silt, mud, and volcanic ash. The blankets of deposits cut off oxygen and slowed the decay of the logs. Gradually, silica-bearing groundwaters seeped through the logs and, bit by bit, replaced the original wood tissues with silica deposits. As the process continued, the silica crystallized onto quartz, and the logs were preserved as petrified wood. Minerals and impurities deposited while the wood was petrifying add the bright colors and interesting patterns.

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