lower mantle


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lower mantle

[′lō·ər mant·əl]
(geology)
The portion of the mantle below a depth of about 600 miles (1000 kilometers). Also known as inner mantle; mesosphere; pallasite shell.
References in periodicals archive ?
The smoother areas of the 660-km boundary could result from more thorough vertical mixing, while the rougher, mountainous areas may have formed where the upper and lower mantle don't mix as well.
In a process known as subduction, which occurs where crustal plates collide, slabs of cold oceanic crust sink all the way down to the core-mantle boundary, making it easy for heat to escape the core through the lower mantle. This cooling mechanism drives the churning convective motions in the outer core that stirs up Earth's dynamo.
We quantified systematically eye numbers on the mantles of sea scallops (Placopecten magellanicus) to determine whether they varied with scallop size (which is correlated with age), or between upper and lower mantles. We predicted (1) smaller scallops, which are more vulnerable to predators, would have more eyes than larger scallops; and (2) because the upper mantle is hypothesized to be in a better position to detect predators, the upper mantle will have more eyes than the lower mantle.
The developments high dense mineral polymorphs in the lower mantle induce cracks, creeps and faults in the lower mantle.
Models with progressively weaker lower-mantle regions (i.e., progressively lower viscosities within the lower mantle) will have shorter decay times, and will thus have reached a state closer to their final equilibrium state by the present day.
(See "Conduits Into Earth's Inaccessible Interior" page 7.) This strongly suggests that distinct geochemical reservoirs exist in the mantle, and seems to favor a layered convection model with different mantle compositions in the upper and lower mantle.
Laboratory tests by Japanese researchers indicated that a huge amount of water may be trapped in minerals in the lower mantle - a thick hot layer extending from 406 miles below the Earth's surface to a depth of 1,800 miles.
As you continue the journey down through the upper and lower mantle, the temperatures increase.
Deeper inside Earth, in the lower mantle or the core, temperatures are too high for diamonds to form.
The most common mineral in Earth's lower mantle is perovskite, a silicate whose crystalline structure can't store many stray hydrogen atoms (which end up in water).

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