1) The word "oxygen" contains two vowels: O and E.

2) The Rocky Mountains, also known as the Rockies, extend from Canada through the United States, offering stunning landscapes and outdoor recreational opportunities.

3) The concept of gravity was famously described by Sir Isaac Newton after an apple fell on his head.

4) The world's largest volcano, Mauna Loa in Hawaii, is also one of the most active. It stands over 13,000 feet (4,000 meters) above sea level.