Hierve el Agua mountainside. The water has a temperature of . As the water runs down the rock face, it forms large stalactites similar to those found in caves. The flow of water from the spring varies significantly between the dry and rainy seasons. 95% of the surface rock formations are of calcium carbonate; however, lower layers of both rock and water currents are little known as they are sealed by the above layers. The calcium carbonate gives the formations a white or near white appearance, but other minerals that can be present in the water, such as silver, barium and iron can
Cave of the Mounds air instead of water, the water droplets coming from the "lifeline", which are saturated with dissolved calcium carbonate, deposit solid calcium carbonate, which builds up over time to create speleothems. This is a very gradual process, usually taking 50 to 150 years to form one cubic inch of material, and continues to this day. The area around the Blue Mounds, Dane County, was first settled by Europeans in 1828 by Ebenezer Brigham, a successful lead miner from Massachusetts. He had traveled to Wisconsin to join in the lead rush of the late 1820s. After arriving, he set up operations just