Block mountain
Also called: Horst · Topic: Geomorphic Processes: Weathering, Mass Movement, Erosion and Soil Formation · NCERT: Class 11, Ch 2 "Structure and Physiography"
Meaning
A block mountain, also called a horst, forms through faulting, which means rocks breaking along cracks called faults. A block of crust either rises between two faults or stays standing while the land around it sinks. The result is a mountain with a flat top and steep sides.
Example
NCERT cites the Satpura range in central India as a block mountain. It lies between the Narmada and Tapi rifts. In Europe, the Vosges and the Black Forest are block mountains on either side of the Rhine rift valley.
Don't confuse with
- Rift valley (graben): here a strip of crust sinks between two faults, forming a valley. In a block mountain, the block stands high.
- Fold mountain: this forms when rock layers bend under squeezing, not when they break along faults.