the time of the physical formation and development of the earth (especially prior to human history)

approximately the last 10,000 years

from two million to 11 thousand years ago; extensive glaciation of the northern hemisphere; the time of human evolution

from 13 million to 2 million years ago; growth of mountains; cooling of climate; more and larger mammals

from 25 million to 13 million years ago; appearance of grazing mammals

from 40 million to 25 million years ago; appearance of sabertoothed cats

a unit of geological time during which a system of rocks formed

The Late Jurassic is the third epoch of the Jurassic period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago.

The Early Jurassic epoch (in chronostratigraphy corresponding to the Lower Jurassic series) is the earliest of three epochs of the Jurassic period.

The Middle Jurassic is the second epoch of the Jurassic Period; it lasted from 176 to 161 million years ago.

The Late Triassic is the third and final of three epochs of the Triassic Period in the geologic timescale.

In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided.

approximately the last 10,000 years

from two million to 11 thousand years ago; extensive glaciation of the northern hemisphere; the time of human evolution

from 13 million to 2 million years ago; growth of mountains; cooling of climate; more and larger mammals

from 25 million to 13 million years ago; appearance of grazing mammals

from 40 million to 25 million years ago; appearance of sabertoothed cats

a unit of geological time during which a system of rocks formed