Two lake-filled maars, Soda Lake and Little Soda Lake, lie NW of the town of Fallon. The basaltic maars were formed subaerially, post-dating the Pleistocene glacial Lake Lahontan, and were estimated to be less than 10,000 years old and perhaps even less than 1,500 years old (Garside and Schilling, 1979; Price and LaPointe, 1998). Soda Lake is about 1.3 x 2 km elongated NE-SW. The 300-m-wide Little Soda Lake lies south of Soda Lake. The late-Pleistocene Upsal Hogback cones lie to the NNE of Soda Lakes. The maars are the site of a geothermal prospect that may have discharged hot springs through the end of the 19th century.