Skip to content

CALS Encyclopedia
of Arkansas

CALS Organizations

Central Arkansas Library System Encyclopedia of Arkansas Roberts Library Six Bridges Book Festival Ron Robinson Theater Rock It! Lab

Browse

Go Back

Entries

All Entries (A-Z) Entries by Category Entries by County

Media

All Media (A-Z) Media by Category Media by County

Overview Entries

Arkansas Overview

Time Period Entries

Pre-European Exploration, Prehistory through 1540 European Exploration and Settlement, 1541 through 1802 Louisiana Purchase through Early Statehood, 1803 through 1860 Civil War through Reconstruction, 1861 through 1874

Post-Reconstruction through the Gilded Age, 1875 through 1900 Early Twentieth Century, 1901 through 1940 World War II through the Faubus Era, 1941 through 1967 Divergent Prosperity and the Arc of Reform, 1968–2022

What's New

What’s New

Get Involved

Teachers/Students

Go Back

Teachers/Students

AR History on the Web Lesson Plans Local Historical Associations Programs on AR History

Activities

Student Activities

History Day

History Day 2025 History Day 2024 History Day 2023 History Day 2022

Other Resources

Other Online Encyclopedias Other Resources

Blog Quizzes What’s New En Español

About

Go Back

About

About the CALS Encyclopedia of Arkansas Mission and Goals Statement Editorial Policies

Volunteers Oversight & Editorial Boards Staff Contact Us Helpful Tips

Support the EOA Search

Entries

Media

All results

- All Media

Geologic Time Scale

Time scale showing geological eras and periods as categorized by the Geological Society of America.

Multicolored "Geologic time scale" divided into time periods on white background

Courtesy of Angela Chandler/Arkansas Geological Survey

Related Entries

Multicolored "Geologic time scale" divided into time periods on white background

About
Blog
Contact Us
Get Involved
Subscribe to Newsletter
Support The EOA

Our Sponsors

Major support provided through a partnership with the Arkansas Department of Parks & Tourism.

Major funding provided by the Winthrop Rockefeller Foundation.

Special thanks to the Department of Arkansas Heritage.

Additional support provided by the Arkansas Humanities Council.

Additional support provided by the Arkansas General Assembly.

Additional support provided by the Arkansas Community Foundation.

Additional support provided by the Charles M. and Joan R. Taylor Foundation Inc.

This project is funded in part by a National Endowment for the Humanities (NEH) Sustaining the Humanities through the American Rescue Plan grant award.

100 Rock Street Little Rock, AR 72201

editor@cals.org

© 2025 Encyclopedia of Arkansas. All Rights Reserved.

Donate

501-918-3025
calsfoundation@cals.org

Ways To Give
Donate Now
Recurring Giving

TRIBUTE GIVING

Honor or memorial gifts are an everlasting way to pay tribute to someone who has touched your life. Give a donation in someone’s name to mark a special occasion, honor a friend or colleague or remember a beloved family member. When a tribute gift is given the honoree will receive a letter acknowledging your generosity and a bookplate will be placed in a book. For more information, contact 501-918-3025 or calsfoundation@cals.org.

The CALS Foundation is a 501(c)(3) organization. Donations made to the CALS Foundation are tax-deductible for United States federal income tax purposes. Read our Privacy Policy.

Contact Encyclopedia of Arkansas

CONTACT FORM

[contact-form-7 id="1017"]

ADDRESS

Encyclopedia of Arkansas
100 Rock Street
Little Rock, AR. 72201

PHONE NUMBER

EMAIL

editor@cals.org

CALS Catalog Login

Login / Signup Get a Card

Login to the CALS catalog!

The first time you log in to our catalog you will need to create an account. Creating an account gives you access to all these features.

Track your borrowing.
Rate and review titles you borrow and share your opinions on them.
Get personalized recommendations.

CALS Digital Services

View All Services

Get an E-Book

Download Music

Listen to an Audiobook

Watch a Story

Download a Magazine

Website and Events Catalog