There is no "first" mountain in the sense that you're asking. Mountains are constantly being formed and eroded, so there's no way to pinpoint the first one.

Here's why:

* Plate tectonics: Mountains are formed by the movement of tectonic plates. These plates constantly shift and collide, creating mountains, volcanoes, and other geological features. This process has been ongoing for billions of years.

* Erosion: Even after mountains are formed, they are constantly being eroded by wind, water, and ice. This means that mountains are constantly changing, and older mountains are gradually worn down.

* Geological timescale: The Earth's history is measured in millions and billions of years. Trying to pinpoint the "first" mountain is like trying to find the first raindrop in a storm – it's impossible to track.

So, instead of focusing on a "first" mountain, it's more interesting to think about how mountains form and the processes that shape the Earth's surface.