What causes a mountain to form?

Answer 1

Earthquakes. Usually small and unnoticeable ones.

Well, actually , its the cracks in the ground that the earthquakes make, then if they accidentaly hit each other, they will form a mountain.

Take the question somewhat seriously please. If you are interested in plate tectonics you know that the continents and sub-ocean plates are in motion. These can cause earthquakes, but that does not cause the mountain to form, just a symptom. For instance the Indian sub-continent is pushing northward into Asia and meeting resistance. The result is uplift and the Himalayan Mountains are formed and still growing. Some mountains are formed when volcanic activity develops as in the Hawaiian Islands.