What are the effects of tectonic shortening and stretching?

Question

What will be an ideal response?

Answer 1

Answer: Compressional stress shortens and thickens the crust by plastic flow in the lower crust and while forming reverse and thrust faults in the upper crust. The principle of isostasy requires the elevation of a shortened region to increase because the thickness of crust increases…Tensional stress thins and stretches the lower crust by plastic flow, while normal faults form in the upper crust. Elevation decreases where the crust becomes thinner. A thinning of the continental crust produces a block that is lower in elevation and whose root shrinks. Isostasy explains why low-elevation rift valleys form where continents lengthen by tension. Isostasy also explains why continents have wide, submerged continental shelves. Continents separate from one another where divergent plate boundaries form. When tension stretches the crust at these divergent boundaries, the crust is also thinner, forming continental shelves with lower elevation than the interior of the continent (where the non-stretched crust remains thicker). The elevation of thinned crust is lower than sea level, causing submergence of part of the continental crust. This application of isostasy explains why a small area of Earth that is underlain by continental crust is also low enough the be covered by seawater.