Geology

The Ironwood Forest National Monument has the densest stands of desert ironwoods anywhere in the world in part due to soil made up of Precambrian Oracle granite. This granite is characterized by large crystal size and it weathers into a coarse, very porous soil that allows deep infiltration of water and air. This porous, well-aerated soil permits tree roots to penetrate deeply to reach moisture. Soil explains much of the lushness of the tree growth in the Silver Bell region.

Of course there is much more to the geology of Ironwood Forest National Monument than the soil that supports desert ironwood trees. Some of the best information comes from a study by our partners at the Arizona-Sonora Desert Museum.

Geologic Aspects of Ironwood Forest National Monument, by Robert Scarborough.