Mantle viscosity

Mantle viscosity is the mantle’s resistance to deformation and flow, commonly estimated near 10²¹ pascal-seconds. It allows solid rock to creep over geological time.

Mantle convection: Slow circulation of solid mantle rock driven by internal heat and buoyancy. Viscous creep lets hot mantle rise and cooler mantle sink over millions of years.
Dynamic viscosity: A measure of a fluid's resistance to shear deformation, expressed in pascal-seconds. Mantle viscosity uses the same units, though the mantle behaves as a creeping solid.
Glacial isostatic adjustment: The ongoing deformation of Earth’s crust and gravity field as the solid Earth responds to changing ice loads. Its postglacial rebound records how quickly viscous mantle material flows beneath the crust.
Glacial isostatic adjustment models: Numerical models that infer solid-Earth structure from deformation and gravity changes following ice loss. Different viscosity profiles can fit rebound data, leaving trade-offs in inferred mantle structure.
Viscoelasticity: Mechanical behavior combining elastic deformation with time-dependent viscous flow. Mantle viscosity describes long-term flow, while viscoelastic models also capture short-term elastic response.
Creep (deformation): Time-dependent deformation under sustained stress, occurring in solids without requiring them to melt. Mantle flow is creep through crystalline rock rather than motion of a liquid.
Pascal-second: The SI unit of dynamic viscosity, equal to one pascal multiplied by one second. The mantle estimate of about 10²¹ Pa·s expresses resistance in this unit.
Postglacial rebound: The continuing uplift of land after the removal of large ice sheets. Uplift rates provide a direct constraint on mantle viscosity beneath formerly glaciated regions.
Seismic tomography: A method that images Earth's interior using variations in seismic-wave travel times. Tomographic temperature and structure estimates help test viscosity models, but do not measure viscosity directly.
Newtonian fluid: A fluid whose viscosity remains constant as shear stress and deformation rate change. Mantle rocks often show stress-dependent creep, unlike an ideal Newtonian fluid.

Linked from 7 pages