Complex sentence: Rocks of the Reading Prong are characterized by elevated concentrations of uranium, the decay of which produces gaseous radon, a potentially hazardous source of indoor contamination in structures constructed on the prong.
Split into simpler sentences: Rocks of the Reading Prong are characterized by elevated concentrations of Uranium. Decay of this Uranium produces gaseous Radon, a potentially hazardous source of indoor contamination in structures constructed on the prong.