Geophysical studies and postseismic deformation analyses confirm that the Earth's mantle viscosity spans multiple orders of magnitude, ranging from approximately 10^17 to over 10^22 Pa·s depending on region, depth, and temperature.
The claim states that the viscosity of the Earth's mantle spans several orders of magnitude. Papers [2] and [6] provide explicit numerical estimates of mantle viscosity across different regions and depths, demonstrating a range from 10^17 Pa·s up to greater than 10^22 Pa·s (a span of five orders of magnitude). Therefore, the claim is strongly supported by the evidence.