The validity of concept that impulsive changes in the volume flux of material rising from the base of the mantle via plumes can cause rapid changes in the heat flux from the core and in the behavior of the geomagnetic field is investigated. It is found that the natural time scale of variations in the heat flux from the core is about 109years, a time scale far longer than that associated with the long‐term changes in the frequency of reversals of the magnetic field; following an impulsive change in plume flux, the heat flux from the core changes on a time scale of several billion years, i.e., on a time scale of the age of the earth. A harmonic variation in the volume flux up plumes results in a similar harmonic variation in the heat flux from the core, but with a phase lag of π/4 and a greatly diminished amplitude. The lack of correlation between mantle plume flux and core heat flux is due to the long natural time scale of the lower mantle and the large thermal inertia of the D″ layer (compared with the heat flux from the core). This calls into question the currently fashionable idea of a direct and immediate correlation between plume volume flux and heat flux from the