Thermal conductivity of lunar and terrestrial igneous rocks in their melting range. 
The thermal conductivity of a synthetic lunar rock in its melting range is about half that of a terrestrial basalt.  The low conductivity and increased efficiency of insulating crusts on lunar lavas will enable flows to cover great distances without being quenched by high radiant heat losses from the surface.  For a given rate of heat production, the thermal gradient of the moon would be significantly steeper than that of the earth.