Horst

Definition

A horst is a fault block, generally elongate, that has been raised relative to the blocks on either side without major tilting or folding. The bordering faults, or fault zones, are usually of near-parallel strike and are steeply dipping, along which the vertical displacement has been approximately equal. Although horsts vary greatly in size, the dominance of a linear upland bounded by faults is a characteristic feature. The derivation of “horst” is from the German term (Stamp, 1961).

General Features

The movements of the blocks that define a horst are relative. All blocks involved may have moved with respect to their original position, but the middle block must have risen more than the outer two. Thus, a true horst in its initial surface form is an elongate structural uplift (Fig. 1A). The flanking lowland areas are quite commonly grabens (q.v.). Under conditions of prolonged denudation, the distribution of variably resistant strata in the fault blocks may be such that the...