The next smaller division of geologic time after era is period.

Here's a breakdown of the major divisions of geologic time from largest to smallest:

* Eon: The largest division of geologic time. Examples include the Phanerozoic Eon (current eon) and the Precambrian Eon.

* Era: A subdivision of an eon. Examples include the Paleozoic Era, Mesozoic Era, and Cenozoic Era.

* Period: A subdivision of an era. Examples include the Triassic Period, Jurassic Period, and Cretaceous Period.

* Epoch: A subdivision of a period. Examples include the Paleocene Epoch, Eocene Epoch, and Oligocene Epoch.

* Age: The smallest formal division of geologic time, representing a subdivision of an epoch.

Let me know if you'd like more information about any of these time divisions!