It has been generally accepted for some time that the earth's mantle is “solid” (crystalline). But increasing complications arise as attempts are made to rationalize that state of matter with the growing list of properties of the mantle.
We suggest that materials of the earth's mantle are in a fourth state of matter, which we propose calling soliqueous—a combination of solid, liquid, and gaseous. It includes elements for forming water molecules and allows expanding superheated steam to supply the principal force for elevating and distorting land masses.
Bridgman's experiments on plastic deformation of materials at very high pressures revealed that spasmodic jerky yielding is characteristic. We propose plastic rupture in shear as the primary mechanism by which energy in the earth is converted to the vibrations of earthquakes.