The acid in the groundwater is, by and large, completely natural. There’s a little bit of carbon dioxide in the air, produced by the respiration of ecosystems and augmented since the industrial revolution by the burning of fossil fuels. Rainwater with dissolved carbon dioxide in it seeps through soil where more carbon dioxide is added to the water by plant root systems. The resulting carbonic-acid solution can dissolve limestone and related rocks.
Chemistry and the water cycle create karst topography. Unfortunately, from time to time, voids open quite suddenly at the surface of the Earth, as was the case under the place where Jeff Bush was sleeping. The Furlows are facing more gradual change, but it’s plenty dangerous. Sometimes underground changes set the stage for results none of us would choose.
Dr. E. Kirsten Peters was trained as a geologist at Princeton and Harvard. This column is a service of the College of Agricultural, Human and Natural Resource Sciences at Washington State University.