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Earth Review 3

name: ______________________________
Across
To release gas.
Period from 1.8 million years ago to present day.
The modern species of humans.
When a large percentage of all known living species die out in a relatively short amount of geologic time.
A gradual process in which something changes into a different and usually more complex or better form.
The second most recent era on the geologic time scale, spanning from 245 m.y.a. to 65 m.y.a; often called the "Age of Dinosaurs."
The geologic era from 570 m.y.a. to 245 m.y.a. that is characterized by an explosion of life.
The death of an entire species.
The geologic era that spans from the formation of Earth around 4.5 b.y.a. to about 544 m.y.a.
Down
The third, and last, period in the Precambrian, that lasted nearly 2 billion years.
Sedimentary layers formed by micro-organisms.
The period that begins about 800 million years after Earth formed and lasted for about 1.4 billion years.
Period from 65 to 1.8 million years ago.
The most recent era on the geologic time scale.
The first period in Earth's history, so named because it was thought to be like Hades.