What are four large section on the geologic time scale?

The largest sections on the geologic time scale are Precambian (which includes the Hadean, Archean and Proterozoic frames), the Phanerozoic (which includes the Palaeozoic, Mesozoic [the well known dinosaur era] and the Cenozoic [the most modern time frame]). After that, take your pick of the smaller subsections of the time scale for the last one. No, actually the answer above states three eras. There are 4, the Precambrian, the Paleozoic with Cambrian, Ordovician, Silurian, Devonian, Carboniferous periods, the Mesozoic with the Triassic, Jurrasic and Cretacaous periods and the Cenozoic with Tertiary and Quaternary.