So far, humans have been lucky to not experience a catastrophe on a global scale. Though they are the most powerful species on this planet, it's easy to forget that the forces that wiped out many successful species in the past are still at work.

Dinosaurs arose as rulers of the Earth 250 million years ago, but their reign soon ended in catastrophe, paving the way for mammals and eventually humans to flourish. Evidence shows that a cosmic impact was responsible, but where did it hit Earth?
 

The most catastrophic extinction event in the history of the earth was the Permian Extinction 250 million years ago. Scientists believe this was caused by a massive half million year eruption in the Siberian traps that lead to wave after wave of toxic gases devastating life on the planet beginning with sulfur dioxide followed by carbon dioxide, hydrogen sulfide and methane. Yet, some animals found sanctuaries where they could survive.
 

Inspired by ideas about nuclear war, a theory that the Earth was encased in ice 650 million years ago has gained popularity in the science community. This program explains how this condition came about, how it ended, the impact on the evolution of animal life and presents the evidence for these conclusions.
 

30 million years after Earth's birth a cataclysmic collision almost destroyed the planet completely. Instead this chance collision formed the moon, triggering an extraordinary sequence of events that formed this unique planet teaming with life.