mantle (redirected from mantle zone)

mantle, portion of the earth's interior lying beneath the crust and above the core. No direct observation of the mantle, or its upper boundary, has been made; its boundaries have been determined solely by abrupt changes in the velocities and character of seismic waves passing through the earth's interior (see seismology). Samples of the upper mantle may be provided by some volcanic eruptions in ocean areas, e.g., the Hawaiian Islands. The continental and ocean crusts, along with part of the solid upper mantle, make up the lithosphere to a depth of about 62 mi (100 km). Within the lithosphere is the Mohorovičić discontinuity, or Moho, considered to be the mantle's upper surface, at depths ranging from 4 to 43 mi (7 to 70 km). Analysis of seismic waves indicates that rocks below the Moho are less rigid and slightly more dense than rocks making up the crust. A zone of low seismic velocity and rigidity just below the lithosphere, called the asthenosphere, is present in the upper part of the mantle, from 62 mi (100 km) to 156 mi (250 km). Its presence is of critical importance to plate tectonics. The mantle continues to the Gutenberg discontinuity at the liquid outer core, with the base of the mantle located about 1,800 mi (2,900 km) below the earth's surface. The entire mantle constitutes about 84% of the earth by volume. Its composition is thought to be similar to peridotite, an igneous rock of mostly magnesium-rich silicate.

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mantle

That part of the Earth that lies beneath the crust and above the central core. On average, the mantle begins about 22 mi (35 km) below the surface and ends at a depth of about 1,800 mi (2,900 km). Predominant in the rock material are olivines, pyroxenes, and the silicate perovskite, a dense form of enstatite.

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mantle

1. Chemistry a small dome-shaped or cylindrical mesh impregnated with cerium or thorium nitrates, used to increase illumination in a gas or oil lamp

2. Zoology

a. a protective layer of epidermis in molluscs that secretes a substance forming the shell

b. a similar structure in brachiopods

3. Ornithol the feathers of the folded wings and back, esp when these are of a different colour from the remaining feathers

4. Geology the part of the earth between the crust and the core, accounting for more than 82% of the earth's volume (but only 68% of its mass) and thought to be composed largely of peridotite

5. a less common spelling of mantel

6. Anatomy another word for pallium

7. a clay mould formed around a wax model which is subsequently melted out

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mantle [′mant·əl]

(anatomy)

Collectively, the convolutions, corpus callosum, and fornix of the brain.

(biology)

An enveloping layer, as the external body wall lining the shell of many invertebrates, or the external meristematic layers in a stem apex.

(engineering)

A lacelike hood or envelope (sack) of refractory material which, when positioned over a flame and heated to incandescence, gives light.

(geology)

The intermediate shell zone of the earth below the crust and above the core (to a depth of 2160 miles or 3480 kilometers).

(metallurgy)

That part of the outer wall and casing of a blast furnace located above the hearth.

(vertebrate zoology)

The back and wing plumage of a bird if distinguished from the rest of the plumage by a uniform color.