<P> The mantle is a layer inside a terrestrial planet and some other rocky planetary bodies . For a mantle to form, the planetary body must be large enough to have undergone the process of planetary differentiation by density . The mantle is bounded on the bottom by the planetary core and on top by the crust . The terrestrial planets (Earth, Venus, Mars and Mercury), the Moon, two of Jupiter's moons (Io and Europa) and the asteroid Vesta each have a mantle made of silicate rock . Interpretation of spacecraft data suggests that at least two other moons of Jupiter (Ganymede and Callisto), as well as Titan and Triton, each have a mantle made of ice or other solid volatile substances . </P> <P> The interior of Earth, similar to the other terrestrial planets, is divided into layers of different composition . The mantle is a layer between the crust and the outer core . Earth's mantle is a silicate rocky shell with an average thickness of 2,886 kilometres (1,793 mi). The mantle makes up about 84% of Earth's volume . It is predominantly solid but in geological time it behaves as a very viscous fluid . The mantle encloses the hot core rich in iron and nickel, which makes up about 15% of Earth's volume . Past episodes of melting and volcanism at the shallower levels of the mantle have produced a thin crust of crystallized melt products near the surface . Information about the structure and composition of the mantle has been obtained from geophysical investigation and from direct geoscientific analyses of Earth mantle - derived xenoliths and mantle that has been exposed by mid-oceanic ridge spreading . </P> <P> Two main zones are distinguished in the upper mantle: the inner asthenosphere composed of plastic flowing rock of varying thickness, on average about 200 km (120 mi) thick, and the lowermost part of the lithosphere composed of rigid rock about 50 to 120 km (31 to 75 mi) thick . A thin crust, the upper part of the lithosphere, surrounds the mantle and is about 5 to 75 km (3.1 to 46.6 mi) thick . Recent analysis of hydrous ringwoodite from the mantle suggests that there is between one and three times as much water in the transition zone between the lower and upper mantle than in all the world's oceans combined . </P> <P> In some places under the ocean the mantle is actually exposed on the surface of Earth . There are also a few places on land where mantle rock has been pushed to the surface by tectonic activity, most notably the Tablelands region of Gros Morne National Park in the Canadian province of Newfoundland and Labrador and Zabargad Island (St. John's Island) in the Red Sea . (Also Macquarie Island, Saint Peter and Saint Paul Archipelago, Troodos Ophiolite, Lizard Complex, Semail Ophiolite, and other ophiolites) </P>

The upper mantle below the earth's crust is known as the