Concerning the extraordinary fires which burn there, I scarcely know what to say, for they possess a strange nature. I have heard that in Sicily there is an immense fire of un-usual power which consumes both earth and wood. I have also heard that Saint Gregory has stated in his Dialogues that there are places of torment in the fires of Sicily. But men are much more inclined to be-lieve that there must be such places of torment in those fires in Iceland. For the fires in Sicily feed on living things, as they consume both earth and wood....
The fire of Iceland, however, will burn neither earth nor wood, though these be cast upon it; but it feeds upon stone and hard rock and draws vigor from these as other fires do from dry wood. And never is rock or stone so hard but that this fire will melt it like wax and then burn it like fat oil. But when a tree is cast upon the fire, it will not burn but be scorched only. Now since this fire feeds on dead things only and rejects everything that other fires devour, it must surely be said that it is a dead fire; and it seems most likely that it is the fire of hell, for in hell all things are dead.
He goes on to describe geysers (one of the few English loanwords from Icelandic):
I am also disposed to believe that certain bodies of water in Iceland must be of the same dead nature as the fire that we have described. For there are springs which boil furiously all the time both winter and summer. At times the boiling is so violent that the heated water is thrown high into the air. But whatever is laid near the spring at the time of spouting, whether it be cloth or wood or anything else that the water may touch when it falls down again, will turn to stone. This seems to lead to the conclusion that this water must be dead, seeing that it gives a dead character to whatever it sprinkles and moistens; for the nature of stone is dead.
But for all the seeming wonders the father recounts, he cautions his son:
Now it must not be regarded as settled that the facts are as we have just said; we have merely tried to bring together and compare various opinions in order to determine what seems most reasonable.
Modern scholars before their time. :-)