The document summarizes the layers and structure of the Earth's interior. It discusses the three main layers - crust, mantle, and core - based on their chemical compositions. The crust is the outermost layer and thinnest, with continental crust thicker than oceanic crust. The mantle makes up most of the Earth's mass and lies between the crust and core. The core is the central part made mostly of iron. It then describes the physical structure, dividing the interior into lithosphere, asthenosphere, mesosphere, outer core, and inner core based on their properties. Tectonic plates consist of crust and the rigid upper mantle, floating on the asthenosphere. Scientists have mapped the interior using seismic waves from earth