In a fault-block system, a Graben is the central block of the Earth’s crust that has subsided or dropped down between two parallel faults. This usually occurs due to tensional forces pulling the crust apart. While the uplifted blocks are called Horsts (mountains), the Graben forms a Rift Valley, such as the Rhine Valley. ANSWER: (B) The subsided block between two parallel faults.
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Block mountains are created by faulting rather than folding. When the crust is subjected to tension, it fractures. A Graben represents the depressed segment that sinks relative to the surrounding land. Geographically, Grabens often form long, narrow valleys with steep walls. A famous example is the East African Rift Valley or the Rhine Graben in Europe. The adjacent elevated blocks that remain standing are known as Horsts. This structural “basin and range” topography is a key study area in geomorphology, illustrating how internal Earth forces can physically pull the lithosphere apart to create lowlands.