Encyclopedia of Earth Science Series - this is a series of subject encyclopedias published by Springer. Some volumes in the series are available electronically, while others are only available in hard copy. The WIU Libraries has the following titles in the series:
Neuendorf, Klaus K. E., Mehl, James P. and Jackson, Julia A., Eds., 2005. Glossary of Geology. Alexandria, Va.: American Geological Institute. This is the most comprehensive dictionary of geological terms.
General Geology Online Dictionaries
Online Dictionaries on Glaciers & Glaciology
Online Dictionaries on Water & Water Resources