What is the crust of the Earth?

Answer 1

The crust is the outermost chemical layer of the Earth, of hard and brittle rock, composed of oceanic crust and continental crust. The crust is typically about 23 miles thick beneath continents, and about 6.5 miles thick beneath oceans. The crust is relatively light and brittle compared to other Earth layers. Most earthquakes occur within the crust.

The crust is composed of igneous, metamorphic, and igneous rock, but primarily igneous rock. The crust is chemically divided into two types. Continental crust is the less dense of the two, granitic in composition, and the thicker of the two. Oceanic crust is more dense, basaltic in composition, and relatively thin. Oceanic crust is being recycled in roughly 200 million year intervals as new crust is being created at mid-ocean ridges and destroyed by the processes of subduction at underwater trenches. The more buoyant continental crust is on average much older, the oldest continental rocks being over 4 billion years in age. Both the oceanic and continental crust are floating on top of the asthenosphere, the physical layer of the upper mantle in which convection currents of heat push and pull the individual segments of crust (known as plates) around. The crust is the thinnest of Earth's layers, comprising a tiny fraction of the planet's total mass.

Answer 2

The crust is the outermost layer of the Earth.