It looks like you're using Internet Explorer 11 or older. This website works best with modern browsers such as the latest versions of Chrome, Firefox, Safari, and Edge. If you continue with this browser, you may see unexpected results.
The GeoWord of the Day is a free service of the American Geosciences Institute. All of the terms and definitions are from the Glossary of Geology, 5th Edition Revised.
Our mission is to help you use our print and electronic resources to find the information you need. Librarians can advise you about research options in person, on the phone, through e-mail, and by using virtual reference chat software.