Researchers have discovered an "unexpected" accumulation of the radioactive isotope beryllium-10, deep underneath the surface of the Pacific Ocean. As detailed in a paper published in the journal Nature Communications,

An unexpected radioactive discovery beneath the Pacific Ocean seabed may provide researchers with a new global geologic time marker. According to a study published on February 10th in the journal Nature Communications, this previously unknown isotopic accumulation may be the result of cosmic disruptions caused by an ancient, near-Earth supernova.

Earth must have experienced something exceptional 10 million years ago. Our study of rock samples from the floor of the Pacific Ocean has found a strange increase in the radioactive isotope beryllium

A strange radioactive 'blip' has been detected deep beneath the Pacific Ocean. Analyzing several thin layers of seafloor crust, scientists in Germany have identified a sudden surge in the radioactive isotope Beryllium-10 sometime between 9–12 million years ago.