|MadSci Network: Physics|
You are on the right track. If the bonfire were hot enough enough heat would radiate downward from it to melt the ice. Of course that depends on how deep the ice is as well. Therefore the simplest answer is yes you can build a bonfire on ice. The fact that heat tends to rise means that the ice is less likely to melt. to completely answer this question, it would be necessary to compute the total amount of heat generated by the fire, and relate this to the amount of heat required to melt one unit of ice, and multiply that by the volume of the ice the bonfire is burning on. Of course the next question is, why build it on the ice? If you build it on ice, presumably you have to carry the firewood farther!
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