TEACHING VARIABILITY OF RADIATION AND RADIOACTIVITY IN GEOLOGICAL TIME AND SPACE

Ionizing natural background radiation on Earth varies spatially by up to two orders of magnitude at present, and its average intensity decreased –for probably most of the time– since before the beginning of biological evolution. Backward extrapolation of the half-life concept indicated the potential for spontaneous fission reactions during the Precambrian even before their reality was proven by the discovery of the Oklo natural uranium reactors. Claims of hazard, damage, or risk to organisms exposed to the upper limits of the natural background range remain unsupported by observable evidence. Radioactivity and radiation (beyond the technical aspects of radiometric dating) must be understood and integrated into the teaching of geoscience in the interest of scientific literacy and integrity. Appreciation of their variability through time and space reduces irrational fears and advances comparative and realistic assessment of real hazards and risks.