What is the Structure of the Earth?
The structure of the Earth is layered, and commonly divided into four parts: the silicate crust, the viscous mantle, the liquid iron-nickel outer core, and the solid iron-nickel inner core. Occasionally, the mantle is further subdivided into the inner and outer mantle, based on differences in rock type, temperature, density, and viscosity. The crust, which is the only part of the Earth that is both relatively cool and completely solid, makes up less than 1% of its total volume. The first part of the structure of the Earth, the crust, consists of cooled rock floating on top of the viscous mantle. The thickness of the crust varies mainly depending on whether it is oceanic (5 km (3 mi) to 10 km (6 mi) thick) or continental (30 km (20 mi) to 50 km (30 mi) thick). The oceanic crust is composed of dense rocks such as gabbro, basalt, and diabase, while the continental crust is made up of somewhat lighter rocks such as granite. The deepest hole ever dug by humans into the crust is 11.26 km (7.
