Jean-Baptiste Panafieu, author of a number of popular science books, gives a clear explanation of mass extinctions.

Two journalists travel to an island in the Arctic Circle where scientists are searching for fossils of extinct animals. Like all journalists, they have a lot of questions: how is it possible for an entire species to completely disappear? Word has it that we're in the midst of a sixth mass extinction, but what exactly does that mean? How did the first five happen? What is the scientific definition of an extinction event?