Why do some of the national parks in the United States resemble the European Alps? Geologist Dr. Robert Darga answers this question.

Why are some rock formations and animals found on more than one continent? The explanation dates back to the Ice Age.

"One" and "ones" can replace nouns, but are not pronouns. They are prop words. Let's look at how they are used.

Geysers represent a very popular tourist attraction in Yellowstone Park. How do they work and where do they come from? And what is sandstone? The video answers these questions.

Watch some coverage of the People's Climate March that was timed to coincide with the UN Climate Summit in New York City. The march was attended by 400,000 people.

This song was written and sung by Bob Dorough. It teaches about the multiplication of 5 through a game of hide and seek, in which the seeker counts by fives.

In this segment, we learn about the role weather plays in the creation of rock formations in the national parks of the United States.

Here are some words to help answer the question "Which one?" We distinguish between singular and plural as well as between something close to us and far away.

In American schools, it's common for kids to have to learn the Preamble to the United States Constitution by heart. This song, from Schoolhouse Rock, is meant to give these kids a hand, even though it is a slightly abridged version.

Jimmy Carter asks Adam Sandler about some biting criticism he had received in regard to his Saturday Night Live appearances. They also talk about the old days, Sandler's various characters, and his movie The Wedding Singer.

We visit Bryce Canyon, where valuable fossils have helped understand the geological history of the planet. The sandstone spires of the canyon are breathtaking.

The BBC looks at a new and innovative renewable energy invention, Kite Power Solutions. It is estimated that 30 kites could provide electricity for 75,000 homes.

The narrator explains how the breathtaking rock formations of Antelope Canyon came to be, and why mountains around the world can provide a metaphor for human existence.

Bob Dignen introduces the topic of decision-making in international companies, and the various approaches to this.

Sigrid explains the meaning of "prop" as both a noun and a verb. Either one can come in handy.