Radioactivity

Radioactivity is everywhere. On earth we are continuously exposed to cosmic radiation from space, and from the earth itself, where radioactive trace materials in the soil release gamma radiation. This is fortunate, for without this radioactivity the earth's core would have long ago cooled to an ice-cold, solid lump of stone; devoid of volcanoes or mountains.

Radioactive elements exist in the soil in very low concentrations. This diminutive radiation forms no

risk to public health, but it can be measured. These measurements supply useful information on

the composition of the soil. Clay, for example, contains more radioactive trace material

than sand. This allows for remote sensing soil properties.