Evolution and the Geological Time Scale

The geologic time scale is a record of the geologic events and the evolution of life forms as shown in the fossil record.

Scientists chose where units of geologic time began and ended based on major changes in ___________________ at certain times.

The first step in developing the geologic time scale was studying rock layers and index fossils worldwide.

Because the time span of Earth's past is so great, geologists use the _____________ time scale to show Earth's history.

Because the time span of Earth's past is so great, geologists use the ​ (a)   to show Earth's history.

Label the Geologic Time Scale in order from oldest to most recent

During which geologic time or era did humans first appear?

The long span of time that begins geologic time is called _____________.

Geologist divided the time between Precambrian Time and the present into three long units of time called _____________.

The Triassic Period, the Jurassic Period, and the Cretaceous Period occurred in the ___________________ Era.