The Unique Unnatural Attractions of Soda Springs, Idaho
Industrial Lava Flows and Geyser-on-a-Timer

1070 Monsanto Slag Pour: "Soda Spring's Man-Made Lava Flow." CLUI photo
THE SMALL TOWN OF SODA Springs, in southeastern Idaho, is home to two unique incidental phenomena, which, though unnaturally formed, resemble their natural counterparts to a remarkable degree.

Several times an hour, the Monsanto Chemical Company dumps red-hot, molten rock down the edge of a dump mound, on its property north of downtown Soda Springs. This attraction is a rare example of man-made molten mountain building. The black hill of cooled slag has formed in the ten years since Monsanto developed this method of slag disposal.

Twenty four hours a day, seven days a week, specialized trucks back up to the edge of the hill, and tip a 600 cubic foot pot of molten slag overboard. The glowing, thousand degree centigrade liquid slides easily down the slope, throwing heat that can be felt hundreds of yards distant. As the liquid cools and solidifies, a crackling, rock-building sound can be heard.

1071 Monsanto's phosphate plant. CLUI photo
The slag is composed of calcium silicate, and is a byproduct of phosphate production at the vast Monsanto phosphate plant. The plant, which consumes roughly as much electricity as Kansas City, produces phosphates which are used in products as varied as soft drinks, insecticides, fireworks, and truck bombs.

1076 Captive geyser viewing platform (upper left) and sign. When winds blow the arrow westward, the geyser is not activated, as it tends to douse the parking lot area. CLUI photo
Three miles south of the slag pour, in downtown Soda Springs, "the world's only captive geyser" spews jets of water 100 feet in the air every hour, or every half hour during the tourist season. The geyser was created in 1937 when a drilling operation accidentally hit a deposit of pressurized gas and water, 300 feet underground. After a few months of uncontrolled spewing, when the town was close to being flooded, the well was finally capped by installing a valve on the casing pipe.

1077 View of geyser portal. The pipe in this photograph actually contains the motor-driven shaft which opens the valve to turn on the geyser. The geyser "blow-hole" is a six-inch diameter pipe which emerges from the underground next to the end of this pipe. CLUI photoIt was decades before the timer was installed to automatically open and close the valve. Up to that point, the geyser had to be turned on manually by special request, a task usually performed by someone from the police department. In the early 1990's, the town decided to develop the site as tourist attraction, and built walkways and a viewing platform over the strange yellow soda deposits next to the geyser pipe.

Similar to the famed Old Faithful and other geysers, the Soda Springs geyser erupts due to pressure created by the combination of carbon dioxide gas mixing with water in an underground chamber. In most geysers, occasional venting through natural fissures in the overlying rock releases the pressure. In the case of the captive geyser, this release is controlled by an electric motor, activated by a timer, which opens and closes the valve at the top of the pipe.