Devils Postpile National Monument and Soda Springs

November 05, 2015


Photographer: Thomas McGuire
Summary AuthorThomas McGuire

Devils Postpile in California is the geologic feature that gives this national monument its name. Soda Springs is located near the main trail to Devils Postpile. The origin of the gas you see bubbling up here in the springs is probably acidic water superheated (above 212 F or 100 C) by subsurface igneous rock that acts to dissolve the subsurface limestone (mineral calcite: CaCO3).

Most of the calcium is deposited as a solid compound where the reaction takes place deep beneath the ground, releasing carbon dioxide (CO2). When this pressurized water reaches the surface (much lower pressure) bubbles of carbon dioxide form, similar to the bubbles in a carbonated soft drink. That’s how this feature got the name Soda Springs.

Minerals containing iron reacting with acids produce the orange-colored deposits. Iron in the spring water oxidizes (rusts) on contact with atmospheric oxygen. The faux credit card at upper right of the bottom photo is shown for scale purposes. Photo taken on October 20, 2013.