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".