Can you help me understand this Science question?

Write a short essay (approximately 200 words) discussing a possible cause for an extinction event. You need not try to explain any particular event, but it should be a real possibility (don’t just use your imagination), so you should make the case that your cause may have happened at least once.

For example, I could whimsically argue that Alien over harvesting of earth creatures leads to mass extinctions. If they take too many krill, then the ocean food chain collapses and worldwide extinctions ensue. Then I could argue the evidence that such an event may have happened in the late Ordovician, and maybe the Pre-cambrian extinction events. So you see, I am interested in you writing about the mechanisms of mass extinctions (something we can anticipate and prepare for), not a history of a particular extinction.

You should explain the cause, how it happens, provide information about how long it lasts, why it kills so many species, and how the earth recovered. You should then extrapolate to today; is it possible for that event to happen now? How would we deal with it?

Avoid using what someone else already posted. If absolutely necessary I’ll accept a duplicate, but there are a lot of theories out there. If you use an event that is already posted and it takes me just 5 minutes to find a unique one, that will affect your grade.

You must also post responses to at least two other people’s event. You can mention if their event is related to your own (sometimes events are linked or have similar sources), or comment on ways of surviving such an event today.