Uh, it's a question with a well-known answer. When uranium and other heavy radioactive elements decay, they often do so via alpha decay. What's an alpha parti

Uh, it's a question with a well-known answer. When uranium and other heavy radioactive elements decay, they often do so via alpha decay. What's an alpha particle? Two neutrons, two protons. Eventually the alpha particle slows down and captures some electrons. What is it now? An atom of Helium-4. If there is radioactive material buried in the earth (there is), and there are geological structures that trap it (there are), then there will be underground deposits of helium (specifically Helium-4). Other than the fact that the same rocks trapping helium can also trap natural gas, though, there is absolutely no further relation between the two. Why would there be? Helium is also found with deposits of radon gas, where no methane is present. BFD.