Encyclopedia of Earth
Encyclopedia of Earth: Geology: Limestone
Article explaining what limestone is, how it is formed, where it occurs, the different types, and how it has been used throughout history. (Published: August 8, 2010)
Smithsonian Institution
Smithsonian Learning Lab: Fossils: Footprints Across Time
Smithsonian Education presents "Fossils: Footprints Across Time." Teachers can download this teaching package that introduces students to the study of fossils. Students will discover what fossils can teach us about the Earth as it was...
University of California
Ucmp: Plate Tectonics
Provides hyperlinks to the history behind and the mechanisms driving plate tectonics. Be sure to click on the globe icons for animations of plate tectonics.