When Hell Freezes Over

Perhaps the most interesting part of the Inferno is (for me) the portrayal of Hell as becoming colder the lower one goes. Common depictions would have one believe that greater depth equals greater temperature. Take, for example, the earth on which we live. The crust and atmosphere, likened to the upper levels of Hell, are cold and wet. The center of the earth, on the other hand, is a hot, molten mess. Considering the thermal opposition of these two settings, why doesn't our poet stick to convention and construct his Hell in accordance with our geologically sound view of the earth?

The most obvious answer to this question is that science hadn't gotten that far when Dante composed the Divine Comedy. No one knew about the molten core of the earth; however, they did know about volcanoes and magma. From where else might lava come, other than deeper in the earth? Why does Dante seek, in light of this recorded natural event, to portray the belly of Hell as frozen? Hailing from Italy would, I assume, only increase the likelihood that Dante was aware of volcanic eruptions, the country situated in a stew of volcanic activity. The only reason I can think of that would cause him to overlook this phenomenon is artistry: it is vital that Dante maintain a legendary and religious aspect to his work, so why not imbue the fall of Lucifer with frigidity rather than heat? Such an approach to this seismic event (literally and figuratively) only increases the chances that his work will catch the eye of the Church and, in turn, its sizable laity. To me (with little background in the religious history of Dante's Italy, mind you), this is as much a literary tactic as a marketing one.