In the paragraph: 
"However, in his subsequent work The Path of the Pole, Hapgood conceded Einstein's point that the weight of the polar ice would be insufficient to bring about a polar shift. Instead, Hapgood argued that the forces that caused the shifts in the crust must be located below the surface. He had no satisfactory explanation for how this could occur."
The last sentence should be removed as it is POV. The term 'satisfactory' in this context without giving any empirical criteria that needs to be met, implies a reaction by the reader to Hapgood's explanation; he or she was not satisfied by his explanation. Instead the editor should present Hapgood's explanation(s) and let the Wikipedia reader decide whether or not it constitutes a satisfactory explanation.