Analysis of the spectral power-density function and the Poincaré method are used to identify the type of motion exhibited by the Earth’s pole from 1900–1990. The former method allows identification of a quasi-periodic regime with two main frequencies — annual and Chandler. The existence of combinational frequencies in this spectrum and the broadening of the spectral peaks suggest a quasi-periodic regime making a transition to chaos. It is concluded that the identification of the polar motion regime over the time interval considered is insufficient to predict the further evolution of the system over arbitrarily long times.