What theVulcanismof the CascadeMountainstellsyouis that this range not onlyhasactivesubduction beneath it, but that the rock layer riding on topis thin.
And the absence of heat coming from the interior means that the moon is an inert lump of rock, bereft of interesting geological processes such as vulcanism.
As Darwin had suggested, heat and electricity were added to the mix to mimic the effects of vulcanism and lightning (later experiments also included light of the ultraviolet variety, to represent the powerful rays of the young sun).