It's tricky to give an exact percentage of the Earth's surface that is made up of mountains, because there isn't a clear-cut definition of what constitutes a mountain.

Here's why:

* Varying Definitions: Some definitions use elevation as a criteria, while others focus on the shape or formation of the land.

* Different Scales: What might be considered a mountain in one region (e.g., a small hill in the Appalachians) could be a mere bump in another (e.g., the Himalayas).

However, we can make some general observations:

* Around 24% of Earth's land surface is considered to be at least 1,000 meters (3,280 feet) in elevation. This includes mountain ranges, plateaus, and highlands.

* Mountain ranges make up a significant portion of this 24%, but the exact percentage is difficult to determine precisely.

In summary: While we can't give a specific number, mountains and mountainous regions cover a substantial portion of Earth's land surface.