<P> "Mesosphere" (not to be confused with mesosphere, a layer of the atmosphere) is derived from "mesospheric shell", coined by Reginald Aldworth Daly, a Harvard University geology professor . In the pre-plate tectonics era, Daly (1940) inferred that the outer Earth consisted of three spherical layers: lithosphere (including the crust), asthenosphere, and mesospheric shell . Daly's hypothetical depths to the lithosphere--asthenosphere boundary ranged from 80 to 100 km (50 to 62 mi), and the top of the mesospheric shell (base of the asthenosphere) were from 200 to 480 km (124 to 298 mi). Thus, Daly's asthenosphere was inferred to be 120 to 400 km (75 to 249 mi) thick . According to Daly, the base of the solid Earth mesosphere could extend to the base of the mantle (and, thus, to the top of the core). </P> <P> A derivative term, mesoplates, was introduced as a heuristic, based on a combination of "mesosphere" and "plate", for postulated reference frames in which mantle hotspots apparently exist . </P>

Where is the mesosphere located in the earth