Horst and Graben

Horst and Graben

A graben refers to a depressed block of the crust whereas a horst refers to a raised fault block of the crust, both bounded by parallel faults, and often appear along with each other.

Horst and graben essentially indicate tensional forces and crustal streching. The two fault lines typically dip toward the center of the graben whereas they tend to dip away from center in the case of a horst.

Their width may range from a few centimeters to several kilometers whereas the vertical movement can go upto hundred and thousands of meters. Several grabens can produce a rift valley whereas several horsts form a block mountain range.

Narmada river valley is one such example of graben, which is result of two parallel faults dipping toward the center of the valley. These two faults are Narmada North Fault and Narmada South Fault. They are surrounded by two horst or block mountain range, Vindhya and Satpura mountain ranges.

The other prominent example of horst and graben in India is lower part of Godavari river valley.