Question

The boundary between the mantle and the core lies at a depth of approximately__________.
A. 3000 kilometers
B. 300 kilometers
C. 1000 kilometers
D. 5000 kilometers

Answer 1

Hint: Earth primarily comprises four layers namely crust, mantle, outer core and inner core.The core–mantle boundary of the Earth lies between the planet's silicate mantle and its liquid iron-nickel outer core.

Complete Answer: The boundary which lies between the mantle and the core is located at a depth of nearly 3000km.

The core–mantle boundary (CMB) is observed through the discontinuity in seismic wave velocities at that depth due to the differences between the aural impedances of the solid mantle and the molten outer core. P-wave velocities are slower in the outer core. S-waves do not occur at all in the liquid fraction of the core.

Hence, the correct answer is option a.

Note:
-The approx. 200 km thick layer of the lower mantle just above the boundary is implied to be the D″ region and is occasionally contained in discussions regarding the core–mantle boundary zone.

-Recent information indicates a distinct boundary layer above the CMB probably made of a novel phase of the basic perovskite mineralogy of the deep mantle named post-perovskite. Seismic tomography researches have shown significant anomalies within the boundary zone and seem to be affected by the African and Pacific large low-shear-velocity provinces.

-The Core-Mantle boundary has also been referred to as the Gutenberg discontinuity.