Mountains are primarily composed of rock, though the specific types and origins vary widely. Most mountains form through geological processes that involve rock: tectonic plate collisions thrust rock upward to create fold mountains, volcanic activity builds mountains from solidified lava and ash, and erosion shapes existing rock formations into peaks and ridges. However, mountains aren't only rock—they also contain soil, sediment, mineral deposits, ice (in glaciated regions), and vegetation. The term "mountain" describes elevation and landform rather than a single material. Some mountains are primarily granite or basalt, others consist of sedimentary layers like limestone or sandstone, and still others are metamorphic rock transformed by heat and pressure. Volcanic mountains contain different rock types depending on whether the eruptions were explosive (producing ash and pumice) or effusive (producing lava flows). Even massive ice sheets and glaciers atop mountains are supported by underlying rock foundations. So while "rock" is the fundamental building block of mountains—without it, we wouldn't have the solid structure needed for elevation—mountains are complex geological features composed of multiple materials and formed by diverse Earth processes over millions of years.