Prior to the present Holocene epoch of Earth history, beginning in mid-Pleistocene time approximately 900,000 years ago, the planet experienced 9 cycles of glaciation and deglaciation, the 100,000 year period of the canonical glacial cycle being characterized by a 
(the planet; experienced; 9 cycles of glaciation and deglaciation, the 100,000 year period of the canonical glacial cycle) (the canonical glacial cycle; being characterized; by a)
the planet the canonical glacial cycle
experienced being characterized
9 cycles of glaciation and deglaciation, the 100,000 year period of the canonical glacial cycle
by a