The topography of the Basin and Range Province evolved in association with a system of roughly north-south trending normal faults. Movements along these faults produced alternating uplifted fault blocks called horsts and down-dropped blocks called grabens. Horsts generate elevated topography, whereas grabens form basins. As Figure 10.13 illustrates, structures called half-grabens, which are titled fault blocks, also contribute to the alternating topographic highs and lows in the Basin and Range Province. The horsts and higher ends of the tilted fault blocks are the source of sediments that have accumulated in the basins created by the grabens and lower ends of the tilted blocks.