A fault-block (or “block”) mountain is formed when a single block of land is split apart into several smaller blocks due to tectonic forces in a fault. The energy released from movement near a fault can cause nearby land blocks to be raised or even tilted. Fault-block mountains refer to the portion of the block that has been raised higher, relative to the surrounding land. These elevated parts are also called horsts.
The splitting apart of the surface also forms valleys and depressions known as grabens, which help to make nearby horsts stand out more. Perhaps the most well-known examples of these types of mountains can be found in the United States. The Sierra Nevada mountain range in the state of California is composed of a series of fault-block mountains. Other examples include the Teton Range in Wyoming and the Harz mountain range in Germany. The tension in these blocks can sometimes cause horsts to topple or tilt, forming stacks of rock. As a result, many block mountains can appear incredibly steep from one side, and gentle and sloping from another perspective. Feel free to make use of our block mountain diagram to improve your understanding on how different mountain types are formed depending on the nature of various geological processes.