Please choose the correct answer to the question: Some localized layers of rock contain the element iridium. Iridium is most often found in space objects such as meteoroids and asteroids. The discovery of these iridium-containing layers has been matched to which phenomena in Earth's history?

Answer1: tectonic plate separations Answer2: mass species extinctions Answer3: orbital path changes Answer4: magnetic pole reversals

Answer format: answer1/answer2/answer3/answer4