The Rocky Mountains began forming in the western United States about 60 million years ago. The Appalachian Mountains and the Rocky Mountains were similar in height when they first formed. Which statements about the Rocky Mountains are true? Select the two correct answers.(1 point)

They are shorter than the Appalachian Mountains.

They are taller than the Appalachian Mountains.

They are younger than the Appalachian Mountains.

They are older than the Appalachian Mountains.