Question

Two students below described a part of Earth's middle layer:

Bob: The deepest part
Joe: The semi-fluid part

Which part of the middle layer did Bob and Joe describe?

They both described the mesosphere.
They both described the asthenosphere.
Bob described the mesosphere and Joe described the asthenosphere.
Bob described the asthenosphere and Joe described the mesosphere.

Answer 1

Bob described the mesosphere and Joe described the asthenosphere.

The asthenosphere is a semi-fluid layer and is always in motion. This movement is caused by the heat in Earth and creates convection currents. Convection currents are circular movements based on temperature and density. The heat from deep inside Earth heats up the semi-fluid particles of the asthenosphere. These particles then become less dense and rise. As they rise to the bottom of the crust, they cool off, become denser, and move back toward the core. Back at the core, their temperature will increase again, causing this circular motion to continue.

The mesosphere is the lower mantle (deepest part of the Earth's middle layer). It is a solid layer about 2,250 kilometers thick and around 2,500 degrees Celsius.

Answer 2

Bob described the mesosphere and Joe described the asthenosphere.

Step-by-step explanation

The three layers of earth are uppermost crust, middle mantle, and an innermost core.

The mantle of the earth has semifluid asthenosphere that is present below the lithospheric mantle. The rocks are in the semi-molten stage due to the higher temperature and pressure conditions.

The deepest part of the mantle is the mesosphere. Hence, Bob described the mesosphere and Joe described the asthenosphere.