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Geologic Eras and Eons
Geologic Periods
Events in Geologic Time
The Geologic Time Scale
100
The geologic Era that lasted the longest, being active from 542 to 251 million years ago.
What is the Paleozoic Era?
100
The first geologic period in history.
What is the Cambrian Period?
100

An event in which many types of living things become extinct at the same time.

What is a mass extinction.

100

A record of the life forms and geologic events in Earth's history.

What is the geologic time scale.

200
The part of the Proterozoic Eon that the Grenville Orogeny took place in, being the metamorphism of bedrock in that area out of early, middle, or late.
What is the late Proterozoic Eon?
200
The most recent geologic period in history.
What is the Quaternary Period?
200

The end of one era and the beginning of a new era is usually caused by a ________ _______________ .

What is a mass extinction.

200

Scientists hypothesize that Earth formed at the same time as the other planets and the sun, roughly _________ billion years ago.

What 4.6?

300
According to the NY rock record, during the Archen Eon, this form was dominant out of sediments and bedrock.
What is bedrock?
300
The name of the period in which the taconic mountains were formed.
What is the Ordovician Period?
300

The subdivisions of eras are called ______________ .

What is periods?

300

Reptiles, such as dinosaurs, were so successful during the _______________ Era that the time is often called the age of Reptiles.

What is Mesozoic.

400
The estimated time (relative according to eon and numerical) of origin of Earth and our solar system.
What is 4,600 million years ago in the early Archean Period?
400
The geologic period that the first form of grass was formed during.
What is the Paleogene Period?
400

What do most scientists think caused the mass extinction at the end of the Cretaceous Period?

What is an object from space struck Earth.

400

Jawless fish were earth's first ______________, or animals with backbones.

What are vertebrates.

500
The amount of geologic periods that took place during the Phanerozoic Eon.
What is 3 geologic periods?
500
The name of the period where a mass extinction of land and marine organisms occurred.
What is the late Permian and early Triassic Period?
500

Earth's atmosphere, oceans, and continents began to form during the first several hundred millions years of ______________ .

What is Precambrian Time.

500

Certain ammonites are used an __________ ___________ because they lived in many different areas but only for a brief time.

What are index fossils. We're actually going to get into these in our next mini-unit.