"There are volcanoes under the oceans spewing incredible amounts of hot gases into the floor of the oceans and much entropy generated from that, which in turn MIGHT be warming the atmosphere as well, over 100s of millions of years."
I think you might be mixing up entropy and enthalpy. The change of entropy is measured by the product of the heat flux and the change of reciprocal temperature. In the case of radiant energy, the starting "temperature" is basically the temperature that could be reached if the light were focussed. That's rather less than solar surface, but its reciprocal is still very low. So the rate of entropy creation is basically solar heat flux times 1/(about 300K).
Solar flux dwarfs anything you can think of - volcanoes, human, whatever. And neither surface heat nor entropy stick around for even years, let alone millions.
If you want to talk about "incredible amounts of hot gases", you really need to look up some numbers.