Rocks are everywhere on Earth, often buried under soil, and are made of minerals like quartz, calcite, feldspars, and micas. Mountains are larger than hills and are formed by tectonic and volcanic processes : Tectonic plates When two continental plates collide, they crumple and fold, forcing rocks up to form mountain ranges. The more the plates collide, the taller the mountains get. Mountains can also form when plates separate and extend. Volcanic activity When magma, or melted rock, erupts from a volcano, it hardens into layers that eventually create a mountain.