Volcano of classifying magmatic volcanoes is by their frequency of eruption, with those that erupt regularly called active, those that have erupted in historical times but are now quiet called dormant or inactive, and those that have not erupted in historical times called extinct. However, these popular classifications—extinct in particular—are practically meaningless to scientists. They use classifications which refer to a particular volcano's formative and eruptive processes and resulting shapes. There is no consensus among volcanologists on how to define an "active" volcano. The lifespan of a volcano can vary from months to several million years, making such a distinction sometimes
Extinct radionuclide long half-lives. A partial list of radionuclides not found on Earth, but for which decay products are present: Notable isotopes with shorter lives still being produced on Earth include: Radioisotopes with half-lives shorter than one million years are also produced: for example, carbon-14 by cosmic ray production in the atmosphere (half-life 5730 years). Extinct radionuclide An extinct radionuclide is a radionuclide that was formed by nucleosynthesis before the formation of the Solar System, about 4.6 billion years ago, and incorporated into it, but has since decayed to virtually zero abundance, due to having a half-life shorter than about 100 million