Tectonic subsidence

Extension and graben systems Where the lithosphere undergoes horizontal extension at a normal fault or rifting center, the crust will stretch until faulting occurs, either by a system of normal faults (which creates horsts and grabens) or by a system of listric faults. These fault systems allow the region to stretch, while also decreasing its thickness. A thinner crust subsides relative to thicker, undeformed crust. Loading The adding of weight by sedimentation from erosion or orogenic processes, or loading, causes crustal depression and subsidence. Sediments accumulate at the lowest elevation possible, in accommodation spaces. The rate and magnitude of sedimentation controls the rate at which subsidence occurs. By contrast, in orogenic processes, mountain building creates a large load on the Earth's crust, causing flexural depressions in adjacent lithospheric crust. Subduction erosion == Environments ==

Tectonically inactive These settings are not tectonically active, but still experience large-scale subsidence because of tectonic features of the crust. Intracontinental basins Intracontinental basins are large areal depressions that are tectonically inactive and not near any plate boundaries. Extensional Tectonic subsidence can occur in these environments as the crust thinning. Passive margins Successful rifting forms a spreading center Forearc basins Forearc basins form in subduction zones as sedimentary material is scraped off the subducting oceanic plate, forming an accretionary prism between the subducting oceanic lithosphere and the overriding continental plate. Between this wedge and the associated volcanic arc is a zone of depression in the sea floor. Extensional faulting due to relative motion between the accretionary prism and the volcanic arc may occur. Abnormal cooling effects due to the cold, water-laden downgoing plate as well as crustal thinning due to underplating may also be at work. ==References==