1. Tectonic Plate Collisions: This is the most common way mountains form. When two tectonic plates collide, the denser plate is forced underneath the lighter plate (subduction). This process creates immense pressure and heat, which can cause the lighter plate to buckle and fold, forming mountains. The Himalayas, for example, were formed by the collision of the Indian and Eurasian plates.

2. Volcanic Activity: Volcanoes, formed by the eruption of molten rock (magma) from the Earth's mantle, can also create mountains. The accumulation of lava flows and volcanic ash over time can build up large cones, forming volcanic mountains. Mount Fuji in Japan is a classic example of a volcanic mountain.