An asteroid crashes into the Earth during the time of the dinosaurs, creating a giant explosion that affects the entire planet. The narrator explains that the asteroid is 6 miles wide and strikes the earth with an impact equivalent to that of 10,000 nuclear weapons. A trillion tons of dirt and rock are thrown into the atmosphere, blocking out the sun for years.
Professor Actual Factual tells Brother and Sister a little about the environment within Bear Country, including the problem of the increasing size of the landfills. He expresses the importance of taking care of the environment through a couple of ways.
This clip provides an overview of dinosaurs, including when they were roaming the Earth and the two main groups that descended from the Archosaurs. It also describes what they ate and how they behaved. This clip then offers some surprising facts about their extinction.
The group comes across a tablet, and Buck explains what it means. He states that it tells the story of several "cosmic cleansings" every 100 million years or so. He warns that another event is coming soon that will wipe out all mammals.