Question at position 8 The ____________ is the layer of Earth's mantle that flows ductilly (plastically) and upon which the tectonic plates "float".inner corelithosphereouter coreasthenosphere单项选择题
A
inner core
B
lithosphere
C
outer core
D
asthenosphere

Question

Question at position 8 The ____________ is the layer of Earth's mantle that flows ductilly (plastically) and upon which the tectonic plates "float".inner corelithosphereouter coreasthenosphere

BlackTom AI · Accepted Answer

Question restatement: The question asks for the layer of Earth's mantle that flows ductily (plastically) and upon which the tectonic plates "float".
Option 1: inner core
This is incorrect because the inner core is the Earth's solid, solidified center composed mainly of iron-nickel. It is not part of the mantle and does not flow plastically; its behavior is solid-state, not ductile flow.
Option 2: lithosphere
The lithosphere includes the crust and the rigid uppermost mantle. It behaves rigidly rather than plastically and does not flow like a fluid layer. Tectonic plates are part of the lithosphere, but they ride on a more ductile layer below, not on the lithosphere itself.
Option 3: outer core
The outer core is a liquid iron-nickel layer beneath the mantle. While it is fluid, it lies below the mantle and is not involved in the ductile flow of mantle rocks that tectonic plates ride on. Its primary role is generating Earth's magnetic field, not plate tectonics.
Option 4: asthenosphere
This is the correct choice. The asthenosphere is the ductile, partly molten portion of the upper mantle beneath the lithosphere. Its plastic flow allows tectonic plates of the lithosphere to move or float atop it, enabling plate tectonics.
In summary, the incorrect options either refer to solid or rigid layers (inner core, lithosphere) or to a layer (outer core) that is not the mantle portion responsible for plate movement. The asthenosphere uniquely fits the description of a ductile mantle layer underlying the lithosphere where plates float and move.

Question at position 8 The ____________ is the layer of Earth's mantle that flows ductilly (plastically) and upon which the tectonic plates "float".inner corelithosphereouter coreasthenosphere单项选择题

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