1. Rocky Mountains: The Rocky Mountains are the youngest of the three, known for their dramatic peaks and overall ruggedness.
2. Appalachian Himalaya: While not an actual mountain range, the comparison implies a similar level of ruggedness as the Himalayas, suggesting they are older than the Rockies but younger than the Appalachians.
3. Appalachians: Being the least rugged, the Appalachians are the oldest of the three. Their peaks have been worn down over millions of years by erosion.
Important Note: While this order is based on the provided clues, it's important to remember that:
* "Appalachian Himalaya" is not a real mountain range. It's a hypothetical comparison.
* Mountain ranges have complex geological histories. The age of a range can vary significantly within its boundaries.
* Ruggedness is not always a perfect indicator of age. Other factors, like the type of rocks and the tectonic forces at play, also contribute to a mountain range's appearance.
