Mantle Viscosity and Genesis Flood Models

When people need to get the oil changed in a vehicle, the word viscosity is likely to be used. To oversimplify, viscosity refers to thickness. Drop a pebble in a glass of water and it sinks quickly. Do the same in a glass of high-viscosity motor oil, it is much slower.

Maybe a geologist slices into a pie and thinks about cutting through the lithosphere and into the magma, but I digest — I mean, digress. Sort of. That liquid rock down below also has viscosity. This affects the thinner areas of the lithosphere.

Viscosity affects not only liquids, but also magma. Secular geologists think deformation is very slow, creation scientists think it was much faster.
Earth crust cutaway illustration derivative, Wikimedia Commons / Washiucho (Public Domain)
Uniformitarian geologists believe this thinning (deformation) is extremely slow, and creation scientists believe it to be much quicker. Secular geologists believe that glacial rebound affects viscosity in certain areas, but it has been shown to be similar in non-glacial areas as well. Creationists use Genesis Flood and the subsequent Ice Age in their models and find that rebound is much more rapid than secular models assumed.
The deformation of the lithosphere and asthenosphere is assumed by uniformitarian scientists to be very slow. The key measure of the resistance of the deformation of the solid earth is viscosity. When a load, like ice, is added to the surface of the earth, the surface is pushed down. When the load is taken off, the surface rebounds upward. Eastern Canada and Scandinavia are currently rising because of the melting of the Laurentide and Scandinavian ice sheets. . . . In biblical earth history, with a short timescale and a different Ice Age history, the upper mantle viscosities would be lower by at least a factor of five. This would imply deformation is faster and operates over shorter-length scales than commonly believed. This would be true in both a catastrophic plate tectonics and an impact Flood model.

To read this technical article in its entirety, see "Earth’s upper mantle viscosity may be lower than assumed."