What are the four major divisions of time on the scale from longest to shortest?

The four major divisions of time, from longest to shortest, are eons, eras, periods, and epochs. Eons represent the largest intervals, spanning billions of years, followed by eras, which last hundreds of millions of years. Periods are subdivisions of eras, lasting tens of millions of years, while epochs are the shortest divisions, typically lasting several million years. This hierarchical structure helps scientists organize Earth's geological history and the evolution of life.