Question

B) Why is the upper mantle called the
asthenosphere?
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Answer 1

Answer:

The asthenosphere is a part of the upper mantle just below the lithosphere that is involved in plate tectonic movement and isostatic adjustments. The lithosphere-asthenosphere boundary is conventionally taken at the 1300 °C isotherm. Below this temperature (closer to the surface) the mantle behaves in a rigid way; above this temperature (deeper below the surface) it acts in a ductile fashion.

Answer 2

Answer:

Explanation:

In my opinion, because some people think that turning a perfectly decent concept into a polysyllabic form with a Greek root proves they are smarter than other people.

However, sometimes, a ‘new’ word to describe something is quite appropriate, because it can be defined to mean THAT ONE THING and only that one thing, so scholars can be more precise.

‘Asthenosphere’ is more descriptive than ‘upper mantle’. The term upper mantle merely tells us where it is. ‘Asthenosphere’ tells us something ABOUT it: ‘astheno’ means ‘weak’ and ‘sphere’ describes the shape. The asthenosphere is the WEAK layer of the earth, where rock material deforms more readily, and where magmas might form.

Of course, they could have just called it ‘weak layer’, and saved a syllable, and made it easier to pronounce and spell, too.