Intectonics,vertical displacement refers to the shifting of land in avertical direction, resulting inuplift andsubsidence.[1] Thedisplacement of rock layers can provide information on how and why Earth's lithosphere changes throughout geologic time.[1] There are different mechanisms which lead to vertical displacement such as tectonic activity, and isostatic adjustments. Tectonic activity leads to vertical displacement when crust is rearranged during aseismic event. Isostatic adjustments result in vertical displacement through sinking due to an increased load orisostatic rebound due to load removal.
Vertical displacement resulting from tectonic activity occurs atdivergent andconvergent plate boundaries. The movement of magma in theasthenosphere can create divergent plate boundaries as the magma begins to rise and protrude weakerlithospheric crust. Subsidence at a divergent plate boundary is a form of vertical displacement which occurs when a plate begins to split apart.[2] As intrusive magma widens therift zone of a divergent plate boundary the layers of crust on the surface above the rift will subside into the rift, creating a vertical displacement of those layers of surface crust.[2]
Convergent plate boundaries create orogenies such as theLaramide orogeny that raised the Rocky Mountains.[3] For this orogen event dense oceanic crust from the Pacific plate subducts beneath the less dense continental crust of the North American plate as they converge. This subduction induced the compression of the bounded western region of the North American plate which created the uplift of different layers of rock. This vertical displacement created the various mountain formations which are cumulatively known as theRocky Mountain range.[3]
Earthquakes are one mechanism that leads to vertical displacement of crust. The fracturing of land during an earthquake creates afault when land is displaced during the event.[4] The throw of the fault is a term used to describe and quantify the magnitude of this displacement.
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Changes inglaciation can lead to the vertical displacement of crust. Glaciers and ice sheets residing on top of landmass result in anisostatic depression, or sinking, in a section of lithospheric crust due to the weight of the ice. Likewise,isostatic rebound, or uplift, occurs when glaciers and ice sheetsrecede.[5]
Using asthenosphereviscosity data researchers are able to determine the rate by which isostatic rebound occurs. Isostatic rebound occurrence rate can be determined by comparing local viscosities to the maximum viscosity of the asthenosphere. Areas with higher viscosity are subject to quick isostatic rebound while in regions of low viscosity crustal uplift occurs at a slower rate. Uplift is still occurring through isostatic rebound from theLast Glacial Maximum.[6]
Glacial isostatic rebound leads to sea level regression which can be measured using14C dating to determine the age ofsublittoral sediment in different regions along the seafloor.[5]
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