Basin and range topography

Basin and range topography consists of alternating parallel mountain ranges and valleys produced by the extension of the Earth's crust, whether from upwelling in the mantle, gravitational collapse, crustal thickening, or the relaxation of confining stress. As the crust stretches and thins it fractures into a series of long, parallel normal faults, and the resulting blocks of rock between those faults subside, uplift or tilt relative to one another, producing the characteristic alternation of mountain and valley; the same thinning crust also lets mantle heat reach and melt rock more easily, which is why the topography is often accompanied by increased volcanic activity.