mantle

Mantle is a term used in science and everyday language to denote an enclosing layer or covering. In geology the mantle lies between the crust and the core; in biology it refers to a molluscan tissue that can form a shell or protect and aid movement; in common speech it can mean a cloak or cape.

Earth's mantle extends from the crust–mantle boundary to about 2,900 km below the surface and is divided into the upper mantle (containing the asthenosphere) and the lower mantle. It is composed mainly of silicate rocks and is heated from below. Mantle convection drives plate tectonics, and the transition zone at 410–660 km depth features mineral phase changes that affect density.

In mollusks, the mantle is the body wall that covers the visceral mass. It secretes calcium carbonate to form shells in many species, while in cephalopods it encloses the organs and powers jet propulsion by expelling water through a siphon. It also participates in respiration.

As a noun, mantle can denote a garment such as a cloak, or a figurative covering or responsibility.