The gently sloping mound around the geyser is travertine. The stone often develops into flights of pools enclosed within little dams.
These dams form through a mix of water and carbon dioxide which makes carbonic acid, and dissolved calcium carbonate.
Carbonic acid is the same weak acid that makes soda water taste slightly sour.
When the carbon dioxide evaporates from a thin film of water on the lip of a pool, a layer of calcium carbonate is deposited because the water becomes less acidic in that particular spot.

The mineral springs in the area were a remarkable phenomenon to pioneers and, for a period of time, made Soda Springs world famous.
A bottling plant was set up at nearby Ninety Percent Spring in 1997.
Huge drums were put over Mammoth Spring, to trap escaping carbon dioxide, which was piped 5 miles over the mountain to the bottling works.
Here the bottles were filled with water from Ninety Percent Spring and charged with gas from Mammoth Spring 5 miles north of here, to make carbonated water.

Bottled water was shipped by the railway carload to eastern markets and to foreign countries, bringing prosperity and fame to Soda Springs. An early ad calls it "the highest class naturally carbonated water in the world."
Known as Idan-ha, the water took first prize at the Chicago World's Fair in 1893