Introduction to Geologic Time Scale

Geologic Time Scale Introduction

Target: You will be able to explain how evidence is used to organize Earth's history into divisions of time called the Geologic Time Scale.

Describing Geologic Change

You have likely changed a lot since you were born. Just imagine all of the changes the Earth has been through since it formed 4.6 bya!

Multiple Choice

The movement of glaciers.

• fast

• slow

Multiple Choice

A tsunami hitting the coast of Japan.

• fast

• slow

Rocks Give Clues About Earth's Past

Major geologic events - such as a super-volcanic eruption, an asteroid impact, or tectonic plate movement - are recorded in the Rock Record.

Fossils Give Clue About Earth's Past

The fossil record is a compilation of all of Earth's known fossils and the information they provide about Earth's history.

Organizing Earth's History

Scientists have constructed a timeline called the geologic time scale. The GTS is used to organize Earth's long history into manageable parts. The GTS is continually updated as new rock and fossil evidence is discovered.

Multiple Choice

As we go further back in the GTS, the less rock and fossil information we have.

• true

• false

The Geologic Time Scale

Earth's history is divided into four major eons which are the longest division of time. Then there are the Eras, periods and epochs.

Multiple Choice

Which is the longest division of time on the GTS?

• eons

• eras

• periods

• epochs

Divisions of Geologic Time

The GTS is broken up into eons, eras, periods and epochs. Divisions in the GTS are not equal. This is because the divisions are based on major events and changes in Earth's history, such as an extinction.

Multiple Choice

What are the divisions of time in order from largest to smallest?

• eons, eras, periods, epochs

• eons, eras, trilobites

• eons, eras, epochs and periods

Multiple Choice

About how long ago did the Jurassic Period end?

• 4.6 bya

• 58 mya

• 138 mya

• 267 mya

Multiple Choice

Which event marks the end of the Permian Period?

• extinction of the dinosaurs

• earliest humans appear

• formation of the Earth

• a mass extinction happned

Multiple Choice

About how long ago did the Cambrian Period end?

• 20 mya

• 250 mya

• 500 mya

• last week

What Eon, Era, Period and Epoch are we living in today?

Eon - Phanerozoic

Era- Cenozoic

Period - Quaternary

Epoch - Holocene

Multiple Choice

What Eon, Era, Period and Epoch are you living in today?

• Phanerozoic, Cenozoic, Quaternary, Holocene

• Triassic, Jurassic, and Cretaceous

• The Cambrian period

Open Ended

How could trilobite fossils be used as an event that changed life on Earth? (think about what we have learned about the trilobite)

Multiple Choice

In what way are eras different from periods?

• Eras are longer spans of time

• They are subdivided into epochs

• They have a longer duration than eons

• They have boundaries marked by mass extinctions

Multiple Choice

What is the approximate age of Earth?

• 4,600 years

• 46,000 years

• 4.6 million years

• 4.6 billion years

Multiple Choice

How does sedimentary rock layers form?

• in large crystals

• in vertical layers

• in swirling bands

• in horizontal layers

Multiple Choice

Earth is approximately 4.6 billion year old. How did scientists determine this?

• measuring the age of the oldest fossils

• measuring the age of the oldest glaciers

• using absolute dating techniques on meteorites

• determining the chemical composition of seafloor sediments

Multiple Choice

What type of organism will we most likely see if we were to visit the Precambrian?

• dinosaur

• humans

• single celled organism

• trilobites