tectonic plate separations mass species extinctions orbital path changes magnetic pole reversals
I gave my students this multiple choice 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?

Only one answer is correct among these 4 choices:
- tectonic plate separations
- mass species extinctions
- orbital path changes
- magnetic pole reversals

Could you tell me which one is correct?

mass species extinctions