Vertical displacement

Tectonic causes of vertical displacement

Convergent plate boundaries create orogenies such as the Laramide orogeny that raised the Rocky Mountains. 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 the Rocky Mountain range.

Earthquakes are one mechanism that leads to vertical displacement of crust. The fracturing of land during an earthquake creates a fault when land is displaced during the event. The throw of the fault is a term used to describe and quantify the magnitude of this displacement.

Glacial isostatic adjustment

Main article: Glacial isostatic adjustment

Changes in glaciation can lead to the vertical displacement of crust. Glaciers and ice sheets residing on top of landmass result in an isostatic 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 sheets recede.

Using asthenosphere viscosity 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 the Last Glacial Maximum.

Glacial isostatic rebound leads to sea level regression which can be measured using 14C dating to determine the age of sublittoral sediment in different regions along the seafloor.

Notes

References

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