The large eruptions which formed the traps were one of the largest known volcanic events of the last 500 million years of Earth history. They continued for a million years and spanned the Permian-Triassic boundary, about 251 to 250 million years ago. It was the same time as the Permian–Triassic extinction event, which is estimated to have killed 90% of species existing at the time. The eruption of the Siberian Traps is a possible cause of this "Great Dying".