For 10 points, name this layer of the Earth between the mantle and the inner core.
Components of the basalt in the Australian Duffer Formation provide evidence that this region is older than 3.4 billion years. That finding is corroborated by the high unblocking temperature of similar components in a South African dacite belt, which show scatter in the parent body rocks that is most readily explained by polarization caused by this region. The sinking of siderophile elements as this region became sufficiently pressurized to melt them constituted the "iron catastrophe," and the place where pressure is sufficient to cause a change of state is the Lehmann Discontinuity, thus signifying one boundary of this region. Convective currents in this region exert the dynamo effect responsible for the earth's magnetic field. This region's complete lack of rigidity, and  hence its inability to transmit shear waves, support the hypothesis that this region is liquid. For 10 points, name this layer of the Earth between the mantle and the inner core.
Components of the basalt in the Australian Duffer Formation provide evidence that this region is older than 3.4 billion years.
the outer core (prompt on "core")