This is a brief overview of the Theory of Plate Tectonics. According to the theory, the Earth's surface layer, or lithosphere, consists of seven large and 18 smaller plates that move and interact in various ways. Along their boundaries, they converge, diverge, and slip past one another, creating the Earth's seismic and volcanic activities. These plates lie atop a layer of partly molten rock called the asthenosphere. The plates can carry both continents and oceans, or exclusively one or the other. The site also explains interaction at the plate boundaries, which causes earthquakes, volcanoes and other forms of mountain building. Educational levels: Intermediate elementary, Middle school
