Mass extinctions, during which many different types of life die out within a relatively short period, occur at roughly 26-million-year cycles.
(many different types of life; die out; T:within a relatively short period; T:Mass extinctions) (Mass extinctions; occur; L:at roughly 26-million-year cycles)
many different types of life Mass extinctions
die out occur
T:within a relatively short period T:Mass extinctions
L:at roughly 26-million-year cycles