What are the two layers below earth's surface in which convection takes place?

Convection occurs in the Mantle and the Outer Core.

The two layers below Earth's surface in which convection takes place are mantle and outer core.
Convection is a form of heat transfer which also includes energy. This happens below Earth's surface in its mantle, which is its interior, and is found between the crust and outer core. And the outer core is fluid and consists mostly of nickel and iron and can be found below the mantle.

Geothermic gradient is the rate of increasing temperature with respect to increasing the depth in the earths interior. away from tech tonic plates boundaries, it is about 25-40 c/km (72-87 degrees f/mi) of depth near the surface in most of the world.