The Hyperion's propellers are hand-cranked by men on the ground. When the entire ship is viewed at rest, the propellers are nowhere near the ground.
Even being within a hundred feet of lava can be deadly, especially in an enclosed area. Not only is the heat excessive, but molten rock gives off toxic fumes.
As Godi gives his vitriolic speech, the fire behind him can clearly be seen through his white hairline and eyes, revealing the shot to be a blue screen effect. He has been superimposed over the background.
Despite Ivarsson's claim that the Vikings speak old Norse, they actually speak a mix of modern Scandinavian languages. Modern Icelandic would have been closer to the authentic tongue.