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Article: Radioactivity
- Article from:
- World of Earth Science
CopyrightCOPYRIGHT 2003 The Gale Group, Inc. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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Radioactivity
Radioactivity originates from extraterrestrial sources and terrestrial geologic sources. All elements with more than 83 protons (i.e., an
atomic number
greater than 83) are radioactive. Some radioactive isotopes also occur in elements with lower atomic numbers.
Atoms that are radioactive emit radioactivity during spontaneous transformation from an unstable isotope to a more stable one. Natural radioactive decay provides a source of heating in Earth's interior that drives mantle dynamics and
plate tectonics
. Both natural and man-made sources of radioactivity at certain levels may represent a significant health risk to humans and other organisms. Radioactive materials ...