crustal thinning

Crustal thinning is a geological process where the Earth's crust becomes thinner. This can occur in various tectonic settings. For instance, at divergent plate boundaries, such as mid-ocean ridges, seafloor spreading leads to the creation of new oceanic crust as plates move apart. This process involves the upwelling of magma and can result in elevated topography due to heat.1

In contrast, crustal thickening is associated with mountain-building processes, like those found in Andean-type belts where oceanic lithosphere subducts beneath continental margins. Here, crustal shortening can occur through overthrusting and folding, leading to thicker crust and significant mountain ranges. Continental crust itself is generally granitic, less dense than oceanic crust, and typically around 40 km thick, forming the planet's land surfaces. Diastrophism, the study of large-scale crustal deformation, encompasses processes like plate movement, volcanic loading, and folding that contribute to these changes in crustal thickness and the formation of major geological features.234