Geologic time begins with a very long span called Precambrian Time. Precambrian Time ended about 544 million years ago. Scientists have organized geologic time into chunks. The chunks of time span different lengths. Using the model, organize the basic units of geologic time in order from longest to shortest.
geologic time, the extensive interval of time occupied by the geologic history of Earth. Formal geologic time begins at the start of the Archean Eon (4.0 billion to 2.5 billion years ago) and continues to the present day.