This area is underlain by the Bigfork Chert, a hard, brittle rock that is extensively fractured and broken as a result of mountain-building activity of the past. Water flows readily through the numerous cracks and pores which penetrate this rock, and there are numerous cold-water springs in the valley. Some of the rainwater is probably collected along the ridges of Arkansas Novaculite which flank the valley. The Novaculite is brittle, and some of it is also quite porous. It was similarly fractured during folding and uplifting.
Rainwater falling into the valley first percolates down through a shallow and rocky soil cover.
Here, it picks up carbon dioxide gas given off by organisms living in the soil. The carbon dioxide dissolves in water, forming carbonic acid. As the rainwater continues to percolate downward through the Bigfork Chert and Arkansas Novaculite, the carbonic acid causes the water to dissolve grains of calcium carbonate scattered throughout the rock. The rainwater is thus gradually transformed into a mildly alkaline, pleasant tasting solution. As the water becomes heated at depth, it also dissolves silica from the surrounding rocks.