Concepts
Isostasy
eye-SOSS-tuh-see
Also Known As Isostatic Equilibrium
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The state of gravitational equilibrium between Earth's crust or lithosphere and the denser mantle beneath it, so that a thicker or lighter crustal block floats higher, much as a taller iceberg floats higher in water.
Isostatic equilibrium itself is well established, but the two classical 1855 models proposed to explain how it is achieved, George Airy's model of uniform crustal density and varying thickness, and John Henry Pratt's model of uniform crustal thickness and varying density, remain in use as different approximations, with the real Earth behaving as a hybrid of both.
Facts
Origin YearThe general term isostasy was coined in 1882 by the American geologist Clarence Dutton. Cross-Tradition Connections
Associated With
Dutton coined the term isostasy in a footnote to his 1882 review in the American Journal of Science, describing the crust's flotation-like equilibrium on a denser substratum.
Originally defined for continental crust and mantle, isostasy has since been interpreted in terms of lithosphere and asthenosphere.
Post-glacial rebound and isostatic depression are phases of glacial isostasy.
In Discipline
A gravitational equilibrium claim about crust and mantle.
In the Other Atlases
- Also in Geography Atlas: Isostasy, the same subject.
Sources
1. Isostasy (Wikipedia)
Wikimedia FoundationLead sectionQuote, Lead section
isostatic equilibrium is the state of gravitational equilibrium between Earth's crust (or lithosphere) and mantle such that the crust "floats" at an elevation that depends on its thickness and density
Clarence Dutton (Wikipedia)
Wikimedia FoundationAssociated With: Clarence Dutton, Isostasy sectionView the Source Dissenting Readings (1 dissenting reading)
Description
George Airy and John Henry Pratt each proposed a model of isostasy in 1855: Airy's model accommodates different topographic heights through changes in crustal thickness with the crust held at constant density, while Pratt's model accommodates them through lateral changes in rock density with crustal thickness held constant. Geoscientists still choose between the two models, or some hybrid, depending on the region and the scale of compensation being studied.
A dissenting reading, from John Henry PrattIsostasy (Wikipedia), Wikimedia Foundation
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