Island 35 Mastodon Island 35 Mastodon The Island 35 Mastodon was discovered on Island No. 35 of the Mississippi River in Tipton County, Tennessee, United States. In 1900, a Pleistocene mastodon skeleton was excavated approximately east of Reverie, Tennessee and southeast of Wilson, Arkansas. In 1957 the site was reported as destroyed. Mastodons are members of the prehistoric, extinct genus "Mammut". They resemble modern elephants. Native to North America, they are said to have lived on the North American continent from almost 4 million years ago, in the Pliocene Epoch, until their eventual disappearance about 10,000 years ago. In 1900, archaeologist James K.
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