Curated OER
National Park Service: What on Earth Is Plate Tectonics?
An easy-to-understand explanation of what plate tectonics is. Contains information about the inner parts of the Earth, the difference between the three types of plates, and numerous maps and illustrations.
Other
University of Delaware: Plate Tectonics
This site is a very simple overview of plate tectonics. It includes a map of all the major plates and a diagram of the layers of the earth.
The Franklin Institute
The Franklin Institute Online: Earthforce in the Core
This site from The Franklin Institute Online takes you to the core of the earth and discusses how volcanoes are formed. Provides links to general volcano information as well as volcano science and teacher resources.